Volume 3 — DISEASES OF THE BLOOD, AND OF THE HÆMATOPOIETIC SYSTEM. (continued 4)

Walshe says: "The order of relative gravity, as estimated not only by their ultimate lethal tendency, but by the amount of complicated miseries they inflict, is—1, tricuspid regurgitation; 2, mitral obstruction and regurgitation; 3, aortic regurgitation; 4, pulmonic obstruction, 5, aortic obstruction."

The following are conditions which render the prognosis in each valvular lesion more or less unfavorable:

In aortic stenosis the prognosis is less grave than in any other valvular lesion. Life may be prolonged and good health enjoyed for many years. Yet it must be remembered that extensive aortic stenosis rarely exists without attendant regurgitation.

So long as the hypertrophy of the left ventricle compensates for the obstruction, the prognosis is good; but when the hypertrophied walls fail to overcome the obstruction, dilatation begins, and the ventricular systole becomes feeble and intermitting, and the arterial supply to the brain is so much diminished as to lead to cerebral anæmia.

If after sudden exertion or violent muscular effort there is interruption or great irregularity in the heart's action, sudden death may occur from a complete arrest of the ventricular systole.

Evidences of excessive hypertrophy and dilatation, the occurrence of syncope, signs of cerebral anæmia, attacks of vertigo, great muscular prostration, continued and marked paleness of the face, and irregularity of the pulse, render the prognosis exceedingly unfavorable in aortic stenosis.

If the presence of vegetations can be determined, there is danger from cerebral embolism.

When there are no evidences of alterations in the ventricular walls after an aortic obstructive murmur has existed for some time, it may be assumed that no vegetations exist on the valves, and that the murmur is not due to extensive aortic stenosis, and consequently is not dangerous to life.

When the mitral valves become involved, the combined lesions render the prognosis unfavorable.

Death may result from cerebral complications, pulmonary oedema, or cardiac degeneration.

Aortic insufficiency is a much graver form of valvular disease than aortic stenosis. It is difficult to estimate the probable duration of life in aortic insufficiency, for it frequently gives rise to no symptom that would lead to its diagnosis until it is far advanced. Twenty-one days and five years are the extreme limits that have been recorded. It must always be borne in mind in estimating the factors for and against a good prognosis that in no other valvular lesion is sudden death so liable to occur. Yet the record of the cases which I have given (page 680) indicates that mitral stenosis is nearly, if not quite, as frequently a cause of sudden death.

A diseased valve can never be restored to its normal functions, and the shorter and more gushing the murmur the more extensive the regurgitation. The effects of the regurgitation must be carefully estimated before a prognosis can be given in any case. When one aortic flap is puckered and shrunken, the other two may elongate and compensate for the patency. But this occurs only in very young subjects.

Aortic regurgitation is, however, more serious in the very young than in adults. In children the valvular changes are less atrophic and more inflammatory in character.

Where the disease is met with in middle life, in those who daily undergo severe mental or bodily strain, the prognosis is unfavorable. And when in such patients there are the evidences of arterial degeneration or a tendency to it, the dangers are greatly increased, for the hypertrophied ventricle drives out the blood from its dilated cavity with greater than the normal force, and the vessels being weakened there is great danger of their rupture; hence the frequent occurrence of apoplexy and infarctions. In the very old I have seen aortic incompetence last a long time and cause little inconvenience.

Again, the prognosis is bad when cyanosis and dropsy result from the failure of a dilated and hypertrophied left ventricle to empty itself. This weakness is the result of that interference with the coronary circulation which brings about impaired nutrition, and therefore degeneration of the heart-walls.

When mitral insufficiency is secondarily induced, then obstruction to the systemic circulation leads to induration of the liver and kidneys, which interferes with the performance of their functions and hastens the fatal issue.

Sudden rupture of a valve or valvular disease that has developed very rapidly is more dangerous than when the valvular insufficiency is slowly developed. The flap or flaps involved can sometimes be determined during life, and then the prognosis will be more or less favorable according as the anterior or posterior are incompetent. In all cases the prognosis depends more upon the condition of the heart-walls and on the general nutrition than upon any other element.

When aortic regurgitation is complicated by aortic stenosis, mitral regurgitation, or by the vascular and visceral conditions resulting from the derangement of the circulation, the prognosis is exceedingly unfavorable. Death may result from embolism, apoplexy, dropsy, pulmonary oedema, from sudden cardiac insufficiency, or from visceral complications. When the radial impulse is felt a little after the apex-beat, it is always important to determine whether the action of the heart remains regular under mental excitement or violent physical exertion: if it does, the prognosis is far better than when it becomes irregular.

Mitral stenosis admits of but slight compensation; if extensive, it is always a grave disease. The prognosis in any case can be estimated by the severity of the thoracic symptoms. When physical exertion greatly exacerbates the thoracic symptoms, the prognosis is especially bad; for during violent exercise such patients are not only liable to pulmonary congestion and oedema, but to pulmonary infarctions and pulmonary apoplexy with large extravasations.

Where mitral stenosis is extensive it ranks next to aortic regurgitation in its danger of sudden death. The statistics furnished by Bellevue Hospital show sudden death to occur as often in mitral stenosis as in aortic reflux.

Congenital mitral stenosis is not dangerous, and does not cause much embarrassment, for it is invariably associated with hyperplasia of the pulmonary arterial system. The later in life mitral stenosis occurs, the more unfavorable the prognosis.

Mitral regurgitation uncomplicated by any other valvular lesion gives rise to very little disturbance of the systemic or capillary circulation. It is more often fully compensated for than any other valvular lesion. The changes which lead to it are of slow growth and their tendency is to remain stationary. Patients with a moderate regurgitation at the mitral orifice suffer very little except during or after violent physical exercise, and, were it not for the slight dizziness which attends it, it would pass unnoticed. As long as the compensatory hypertrophy of the right ventricle is sufficient to overcome the obstruction to the pulmonary circulation, patients with this form of heart disease may not suffer from dyspnoea even after violent physical exercise. As regards the duration of life, the prognosis in mitral regurgitation is good. When, however, mitral stenosis and regurgitation coexist, the liability to sudden pulmonary complications becomes so great that a very guarded prognosis must be given; and it must be remembered that combined reflux and stenosis at the mitral orifice is a frequent combination.

In very many instances it is unnecessary to tell a patient with mitral reflux that he has an incurable heart disease, for with no other valvular lesion the individual may live to advanced life. But when it is combined with mitral stenosis it must be regarded as a very serious form of valvular lesion. As soon as symptoms occur that show failure of the right heart, the prognosis becomes unfavorable. Oedema of the extremities or fluid in any of the serous cavities, cyanosis, dyspnoea, and hæmoptysis, are indications of such failure.

Death may result from general anasarca, from serous effusions into the pleuræ, peritoneum, or pericardium, from pulmonary oedema and congestion, or from heart-insufficiency.

Extensive obstruction or regurgitation at the pulmonic orifice would necessarily lead to serious results, but there are no reliable data upon which the prognosis can be based.

The prognosis in tricuspid obstruction and regurgitation, when associated with mitral disease, is very grave; but it is not as bad as when it results from chronic bronchitis and pulmonary emphysema.

When in any case jugular and epigastric pulsation are marked, the changes in the various organs of the body already referred to rapidly ensue. Walshe says that "tricuspid regurgitation is the worst of all valvular lesions." Patients with tricuspid reflux are in extreme danger from intercurrent attacks of acute pulmonary hyperæmia.

Tricuspid disease, of all valvular lesions, leads most rapidly to cyanosis and dropsy.

TREATMENT.—The treatment of aortic stenosis and of aortic regurgitation may be summed up under three heads—viz. rest, diet, and regimen.

Rest is most important; it must be mental as well as physical; the appetite, emotions, and passions must be kept under perfect control: these indications are best maintained by a sedentary country life. Straining, especially when the hands are above the head, should be carefully avoided.

The stomach also must have all the rest compatible with the most perfect nutrition; it is frequently a difficult matter to combine both indications, for it should be remembered that the more perfectly the nutritive processes are maintained the longer will the cardiac muscle resist degeneration. Sugar, sweet vegetables, and animal fat must be sparingly indulged in. The food should consist of nitrogenous, albuminoid material, and should be taken in quantities that do not disturb the heart's action.

In aortic incompetence patients in sleeping should assume, as nearly as possible, a horizontal posture. By lying on their backs they lower the height of the distending column of blood, and thus relieve both the cardiac circulation and the tendency to pulmonary congestion. Sometimes, when defective aortic pressure reacts injuriously on both the gastric and hepatic secretions and limits both their supply and their efficiency, moderate alcoholic stimulation may be cautiously employed to tide over a weakly period. The bowels should be gently moved once daily. That the cutaneous circulation may be active the body should be warmly clothed. Any prolonged exposure of the surface to cold is to be avoided. In winter the warm bath may be occasionally used, and in summer the patient is frequently benefited by a warm sea-water bath.

Medicinal agents are not to be resorted to until the cardiac hypertrophy fails to be compensatory. Then relief is demanded for the failing heart-power. In aortic regurgitation with feeble heart-action the tincture of digitalis and the tincture of the perchloride of iron are to be given in ten-minim doses three times a day. The iron is especially indicated whenever anæmia is evidenced. Digitalis is given to produce a sedative action, and therefore should be given in very small doses and regulated according to its effects on each patient. An infusion of the English leaves is the preparation which is most reliable, although the tincture, if fresh and well prepared, is equally good. When rapid and immediate action is demanded, digitalis may be given hypodermically. There is one guide to its use not unimportant to remember: that is, as long as it causes an increase in the flow of the urine it is safe to continue its use. When vertigo and syncope are prominent symptoms quinine and strychnia may be given with the digitalis. When the heart in aortic reflux acts with violence and rapidity, and the arteries are in a state of high tension, aconite will be found of service in quieting the heart's action. In aortic incompetence small doses of arsenic seem to have a stimulating effect, especially when given with digitalis and iron. Iron may disturb the stomach, arsenic seldom if ever does. It is always a safe rule when giving iron to administer at the same time a bitter vegetable infusion, as quassia or columba.

When the hepatic and gastric vessels are engorged, three or four leeches over the liver or epigastrium, followed by a warm fomentation, will afford temporary relief.

At no time should a large quantity of fluid be taken into the stomach. Symptoms of angina pectoris, with local pain and dyspnoea, are evidences of aortitis. This demands the application of leeches over the sternum and continued small doses of mercury.

The treatment of dyspnoea, dropsy, pulmonary oedema, and other late and distressing symptoms will be considered in connection with mitral disease. Sometimes the pain of aortic disease is so severe as to require an anodyne for its relief: opium must not be given by the mouth, but the sulphate or the hydrochlorate of morphine can be safely given hypodermically. The severe angina-like pain of aortic regurgitation can often be promptly relieved by the nitrate of amyl.

Barlowe and Fagge both advise senega and ammonia carbonate for the less severe effects of aortic reflux. They advance no reason for the use of these drugs, but their cases show that they have a markedly beneficial effect. All authorities unite in regarding aortic insufficiency as less amenable to treatment than other valvular lesions.

In all cases the idiosyncrasy of each patient should be carefully considered.

No treatment can restore a diseased valve to its normal condition, or prevent, for any considerable time, cardiac dilatation and hypertrophy when the normal function of the valves is greatly interfered with.

The first step in the treatment of a serious lesion at the mitral valves is to make the patient clearly understand his exact condition, that he may see the reasonableness of the advice given, for his treatment for the most part must be carried on by himself. A patient must be fully persuaded of its necessity before he will regulate his habits and mode of life in accordance with the requirements of his case. The rules as to nutrition are the same as those to be observed in aortic stenosis and reflux. There should be a gentle and regular daily evacuation from the bowels. Straining at stool must be avoided, and any use of alcohol, strong tea, coffee, and tobacco is to be prohibited. If in either form of mitral valvular disease the patient is anæmic, iron should be given. This is given as a food to such patients, and is best administered about half an hour after meal-time. Ten or twenty grains of Vallette's mass may be given with benefit to anæmic patients two or three times a day for a long period.

Patients with mitral reflux should avoid a prolonged use of the voice, especially in speaking or singing. Small doses of quinine and strychnine, alternating with the administration of iron, are often of service. If there is anorexia, infusion of quassia or columba may be given with the iron. The triple phosphates of iron, quinine, and strychnine, or small doses of dilute sulphuric acid, will be found to improve the condition of these patients when they show signs of extreme debility.

In every case of mitral disease there comes a period when the pulmonary hyperæmia shows that the compensation of the right heart has failed. An adjustment of the heart to the circulation is now effected by the judicious administration of digitalis. Digitalis should only be given at those times when the heart-failure is imminent and there is marked pulmonary congestion. Half an ounce of the infusion every two hours for twenty-four or forty-eight hours is often required to overcome the heart-failure. The time will come when digitalis ceases to have its sustaining effect upon the heart-muscle; hence it should always be most sparingly and carefully used, and the patient should never be allowed to use it continually.

When the pulse is rapid, feeble, and irregular, more time is needed for the flow of blood into the ventricle, and greater force and regularity in the ejection of the blood from that ventricle are demanded. Digitalis fulfils all these conditions: the pulse becomes regular, beating about sixty per minute, full and forceful. The urine, before scanty, now becomes abundant and normal. Pulmonary engorgement diminishes, and commencing dropsy gradually but totally disappears.

Hayden advises ten minims of the spirits of chloroform and fifteen minims each of the tincture of digitalis and the tincture of the perchloride of iron in an ounce of water every three hours.

Whenever asystolism is present or suppression of urine is threatened, digitalis should be given whether the other indications are present or not. In most cases of mitral stenosis it is best to avoid the use of digitalis as far as possible.

The dropsy which accompanies advanced mitral regurgitation may be promptly relieved by compound jalap powder, combined with calomel in sufficient quantity to produce prompt and free catharsis. In some cases of cardiac dropsy, squill, juniper, brown cream of tartar, and copaiba act as diuretics. This latter drug is best exhibited in the form of the resin.

In mitral reflux a combination of digitalis and nitrous ether will often be found to act as a diuretic. In all cases when a diuretic is given in heart disease the loins should be cupped or warm poultices applied and the bowels freely purged. In copious hæmoptysis in cardiac disease ergotin may be given in full doses either by the mouth or hypodermically.

The hæmoptysis which accompanies pulmonary apoplexy of heart disease sometimes temporarily relieves the dyspnoea. On this basis Dickenson and Fagge and other English writers recommend venesection for the relief of the pulmonary engorgement or heart-failure. Pain in the præcordial region which accompanies valvular insufficiency may sometimes be relieved by the application of leeches over the præcordial space. Hyoscyamus, hydrochlorate of morphia, nitrate of amyl, chloroform, and a belladonna plaster over the præcordial space have all been employed for the same purpose.

It is to be remembered that such pain is the cry of the heart-muscle for a higher degree of nutrition.

Bleeding in heart disease favors dropsy by thinning the blood and by diminishing the heart-power. It should never be resorted to except in great emergencies. Niemeyer advises arsenic and antimony in mitral valvular disease, but does not say in what cases or for what reason they are to be used. When in the late stages of mitral disease the free use of digitalis fails to regulate the pulse and to relieve the pulmonary engorgement, its prolonged administration does harm rather than good; but in every case of mitral disease where the drug has not been used it may be safely affirmed that its administration will give prompt relief.

If it becomes necessary to use an anodyne or hypnotic at any period in the course of mitral valvular disease, morphia hypodermically is to be preferred to all others.

The rules in regard to hygiene, diet, and exercise which have been given for the management of mitral disease are equally indicated in the management of pulmonary obstruction or regurgitation. Beyond this their treatment is purely symptomatic.

The treatment of tricuspid obstruction depends upon the gravity and sequelæ of the accompanying disease—viz. mitral. Stenosis of the tricuspid orifice never occurs until mitral obstruction is excessive, and the latter condition is always the predominant one.

The same rules of hygiene and diet which have already been given for mitral disease must be followed with the utmost care by those suffering from tricuspid reflux. The patient must lead a life of perfect quiet, and should live in a warm, equable climate. When occurring with mitral disease digitalis should not be omitted; for although the drug, by increasing the action of the heart, would seem to be injurious, yet it promotes ventricular contraction, and thus tends to relieve the tricuspid pressure. In tricuspid insufficiency with pulmonary emphysema this drug should be very cautiously exhibited, and its use or omission must depend upon the effects produced in each case. If the cerebral symptoms are exaggerated, it must be discontinued. The indications for the use of tonics, such as iron, quinine, strychnine, are the same and follow the same demands as in mitral disease. When venous engorgement demands prompt relief, drastic cathartics or the abstraction of a few ounces of blood from the arm will temporarily diminish the high venous tension. The treatment of the dropsy and the local oedema is the same as for similar condition occurring in mitral disease. There are many subsidiary remedies which will have to be employed for the relief of gastric, hepatic, and intestinal symptoms, which are often the most troublesome occurrences of this disease.

CYANOSIS AND CONGENITAL ANOMALIES OF THE HEART AND GREAT VESSELS.

BY MORRIS LONGSTRETH, M.D.

The questions involved in the subject of the congenital defects of the heart and its great vessels and their causes are not easy of settlement. In the first place, the seat, the extent, and the consequences of the deficiency or defect are not regular or constant. Secondly, the causes and the mode and date of their origin are involved in great obscurity. Their classification either on a purely topographical or on a purely etiological basis is almost impossible on the one hand, because the changes are so irregular and varying, and, on the other hand, because our knowledge of the primary cause or causes of the alterations is quite defective. The views which at the present time find most favor arrange the various malformations into classes according to the period of development of the foetus at which the arrest or change of tissue occurred—as it were, a chronological classification. The ideas in respect to the pathology or the pathological causes of malformed hearts have undergone great changes—changing in some degree pari passu with the mode of classification, and in great degree inducing and compelling such changes.

In early times deformed hearts were looked upon as monsters, curiosities, lusus naturæ. When a knowledge of foetal development and circulation was acquired the deformed heart was compared with the heart-formation in classes of a lower grade than mammals. Such were the beliefs of comparative anatomy and physiology that it was held that the human foetus was matured by stages from the forms found in the lowest invertebrates through the various ascending scales of the animal kingdom. This classification was, on the basis of comparative anatomy, purely anatomical. The underlying thought of such pathological teaching was that in the original ovum something was left out—an actual deficiency of parts which, when developed in the natural manner, made man different from the lower animals; or else, supposing these parts to have been originally present, there was a defect of plasticity, causing a failure of the proper adhesion of symmetrical portions. Excessive development was looked upon as a surplus of parts in the ovum, and by their growth certain of the openings of the heart were prematurely closed. In this view of the pathological alterations no expression of opinion was made how the excess or deficiency of structure was occasioned: the malformation was merely a failure of the parts to rise and pass through the various grades of development—a too rapid or a too slow growth of one or more of the various parts of the foetal heart. There was no reason assigned why the human ovum had in it deficiencies or excesses of material, and thus came to resemble in one of its parts the conditions found in lower animals.

About 1850, Dittrich of Erlangen, by his studies of inflammation of the heart during intra-uterine life, quite diverted public opinion from the older views of the subject. Peacock's earlier studies preceded this work by a few years, and a few years later came Meyer,¹ who greatly extended the scope and influence of the inflammatory theory of Dittrich. Ten years later commenced the clinical recognition of congenital heart defects, and especially the anatomical changes in congenital narrowing of the pulmonary artery, by Von Dusch and by Mannkopff,² and by Stoelker.³ Friedberg had, however, as early as 1844, published his studies of the stages of development of the circulatory organs in the human embryo, and had in accordance therewith divided the malformation of the heart into three groups, corresponding to the three periods of the heart's growth. This was the classification adopted quite independently by Peacock of London in his first publication in 1857. It was not until after Dittrich's studies⁴ and Meyer's that any distinctive cause was assigned for the failure to develop.

¹ Virch. Arch., Bd. xii., 1857.

² Ann. des Charité-Krankenh. zu Berl., 1863.

³ Diss., Bern, 1865.

⁴ See Dorsch's (his student) dissertation, Die Herzmuskelentzundung als Ursache angeborner Herzcyanose, Erlangen, 1855.

Carl Heine,⁵ and also Halbertsma, proposed a classification based on the quantitative and qualitative differences. Under the first division the former placed such changes as absence of the heart, deficiency of individual parts, abnormal smallness, atresia, and fissures; and, in the other direction, duplication of the heart as a whole or in its individual parts, and abnormal largeness. The qualitative differences were deviations of form, of position, and of the arrangement of the great vessels.

⁵ Angeborene Atresie d. Ostium arteriosum dextrum, Beitrag z. Lehre v. d. angeborenen Herzanomalium, Tübingen, 1861.

Peacock's classification in his earlier edition (1858) was partly on the basis of the time at which arrest of development occurs, and partly on the degree of impediment to the circulation and the functions of the heart. In his second edition he adheres to the same classes, with slight modifications, thus: 1. Arrest of development early in foetal life (fourth to sixth week; heart with two or three cavities; single or imperfectly divided arterial trunk); 2. Arrests at a later period (sixth to twelfth week; imperfect auricular or ventricular septa; imperfect or misplaced vessels); 3. Those after the third foetal month (closure and patency of foetal passages; irregularities of valves, cavities, etc.).

Kussmaul (1865) published a very important work on malformations due to defects of the pulmonary artery,⁶ and these malformations he considers under two general groups—viz. those having their origin before the ventricular septum closes, and those occurring after this period. His most valuable contribution to the subject is the importance which attaches to the distinction between primary and secondary defects or arrests of development—i.e. between an original alteration of growth or morbid condition, and those which follow from it as a necessary consequence. Of his classification, and of the importance of pulmonary artery malformations, a further description will be given.

⁶ Ueber angeborene Enge und Verschluss der Lungenarterienbahn, Freiburg, i. B.

For study, one would wish to arrange the malformations in classes convenient for clinical purposes. For example, separate them into groups of the defects compatible with extra-uterine existence and those incompatible with adult life. Unfortunately, this division is not possible. We find many cases of defects involving originally the same seat: in one the individual lives many years, in another the obstruction immediately induces symptoms, and death soon comes. A classification according to the seat of the disease alone, if it could be made, would give the subject a simplicity equal to that of valvular heart disease in the adult. Here, however, we find such variations in the details of the alteration that if this principle of classification alone is employed the confusion becomes very great. It would seem, therefore, that the principle first made use of by Kussmaul, of classifying the defects by distinguishing the primary malformations from their secondary effects, renders the subject the most simple, and at the same time affords the advantage of more readily understanding the mechanism of their production.

It will be useful to pass over seriatim, following the course of the foetal circulation, the various valves, orifices, and foetal openings to be able to comprehend which are most liable to defects or to see which defects most frequently occur, and also to find which alterations produce the greatest disturbance of the circulation.

1. The Foramen Ovale and Septum of the Auricles.—In markedly deformed hearts the entire septum may be in greater or less degree wanting, as seen in cases of the bilocular or trilocular organ. This defect is comparatively rare, and the foetus has but a short extra-uterine life. In other cases the septum is complete, but the foramen may be unusually large, and remain unclosed wholly or in part; perforations may be present, or the valve may merely fail to adhere. Of the latter cases, the patent foramen is found in conjunction with defects at other parts, while small sieve-like perforations or the mere non-adherence of the membrane—both of very common occurrence—may be owing to a temporary obstruction during the early hours of life or to any unknown cause, or may possibly be due to a reopening of the foramen from an acquired disturbance of the circulation. Opinions vary as to the mechanism of the closure of the foramen. Some consider it a passive process due to increased blood-pressure in the left auricle, coming from the entrance of the current of aërated blood from the lungs; others speak of it as an active process resulting from the excitation to contraction of the muscular fibres in the membranous valve. Whatever may be the mechanism, patency of the foramen ovale of undoubted foetal origin (excepting the minute perforations and oblique slits) must be looked upon in nearly every case as a secondary defect—secondary to an obstruction to the outflow of blood from the ventricles through the great arterial trunks, or it may be from the auricle itself through defect of the auriculo-ventricular orifice. In a vastly preponderating number of cases it results from pulmonary artery obstruction. The foramen may close, however, in such a case if an outlet is provided by the aorta through an open septum ventriculorum, or when this vessel arises from both ventricles. Narrowing or closure of the right auriculo-ventricular orifice, as a primary cause, can prevent the closure of the foramen ovale; primary narrowing of the tricuspid orifice is very rare, single or combined with other defects. In these cases the direction of the blood is from the right auricle to the left. There are, however, cases on record of patency of the foramen ovale in which the blood-current is from the left to right side, the reverse of the foetal course. Here the cause to be looked to is a congenital deficiency of the mitral orifice, or a narrowing, closure, or malposition of the aorta.

2. The Right Auriculo-ventricular Orifice and Tricuspid Valve.—A primary deficiency of this orifice and the valve guarding it very rarely occurs as a primary defect and uncombined with malformation of other parts of the pulmonary circulation. It does come in certain cases in conjunction with great narrowing of the pulmonary orifice or artery, but by no means commonly. If the pulmonary outlet is normal and in the usual position, the right auriculo-ventricular orifice is never found closed, although the leaflets have been seen defective, permitting regurgitation. In certain other cases the orifice and valve, as well as entire right ventricle, show a failure to develop, and all these parts appear shrivelled. This condition is a secondary result, due to a great deficiency of the pulmonary artery and narrowing of the pulmonary conus. The malformation of the pulmonary artery in such cases results from an unequal division of the truncus communis—the narrowing of the conus generally from endo-myocarditis. The aorta is unusually large in diameter. The blood from the right auricle passes through the foramen ovale to the left side of the heart; the ductus arteriosus Botalli remains open, or in very rare cases the mixed venous blood reaches the lung through collateral channels. In rare cases the blood, in addition to the open foramen ovale, has a direct passage from the right auricle into the left ventricle.

3. The Pulmonary Artery and the Right Conus Arteriosus.—This situation presents by far the largest number of cases of congenital heart malformation of primary occurrence. The defects at this part require different interpretations according as they are found within the right ventricle or in the pulmonary artery itself. So frequent are the defects at these seats that Kussmaul bases his classification, for a large proportion of cases, on the malformation of the pulmonary artery track, and describes them as combined with defects secondarily resulting in other parts.

The narrowing or closure may exist either at the limit between the sinus and the conus of the right ventricle, the conus arteriosus may be uniformly narrowed, or the defective development may involve the orifice only or the whole length of the pulmonary artery. Many of these defects, resulting in closure or narrowing, are due, as Rokitansky was the first to show, to inflammatory changes. It is Kussmaul's great merit to have pointed to the fact that a very large proportion of all malformations owe their origin primarily to diseased conditions originating at this seat. The varieties of these defects and their secondary consequents will be described later.

4. Patency of the Septum Ventriculorum.—The degree of deficiency of the septum varies greatly. The entire partition between the ventricles may be wanting or exist in merely a rudimentary condition. Ordinarily, there is found a triangular, rounded, or oval opening in the septum close to the base of the heart, at the portion which in the normal heart consists of only a membrane (pars membranacea). Besides this usual opening, one, or even two, others may present themselves at other points of the septum, thus forming multiple communications between the cavities. In narrowing or closure of the pulmonary passage the septum is more or less deflected toward the left ventricle to allow a freer passage of blood from the right side of the heart through the open septum into the aorta. In other cases the passage of blood may be from the left ventricle into the right—the reverse of the usual direction. The defects of the septum are usually of a secondary character, dependent on primary malformation of other parts, and, as already said, chiefly those of the pulmonary track. They are of congenital origin, commencing early in foetal life, before the third month, when normally the septum closes. Hence patency of this septum furnishes in many cases a valuable means of determining the date of the primary defects with which it is found combined. This malformation, however, does very rarely stand as an isolated defect, and still more rarely it is believed to have been acquired through an ulcerative destruction (myocarditis) of a portion of the septum, either during foetal or extra-uterine life; wasting or atrophy of the membranous part is sometimes thought to have occurred. In these latter cases a misdirection of the blood-current of a marked sort rarely occurs unless the inflammatory or other changes affect the main arterial orifices.

5. The aortic and mitral orifices are very much less frequently found narrowed or obstructed as the result of congenital primary defects than the orifices and their valvular apparatus of the right heart; and, also following the rule which obtains on the right side, the mitral is less frequently affected than the aortic orifice.

6. Of the Malformations of the Great Vessels.—Such changes may come alone, though usually they are combined with simultaneous or consecutive defects in other parts of the central circulatory apparatus. Of the sorts of defects or malformation which these two vessels suffer, there are two chief forms to be described: 1, such as result from an unequal division of the vessels in their formation from the truncus communis; 2, those which result in more or less complete transposition of their origins. Of the transpositions we may find two sorts: in one the vessels maintain nearly their normal relative positions to each other, but each communicates with the improper ventricle; in the other they are transposed relatively to each other and also to the respective ventricles. In the first of these classes, unequal division, one variety may be ascribed to a defective or irregular development of the septum by which the vessels are formed of unequal sizes; the other, originating later in foetal life—i.e. after the third month (for the septum between the vessels is completed nearly simultaneously to the ventricular septum)—results from inflammatory or other morbid change in or about the orifice and trunk of one or other vessel, causing a narrowing or closure, the other vessel showing compensatory enlargement. This form is not a true unequal division of vessels. The apparent origin of one or both vessels from the same ventricle in these cases is not a true example of transposition of the vessel, but is due to a deviation of the septum ventriculorum toward one side or the other from increased blood in the ventricle from which the outflow is more or less completely obstructed. True transpositions of the vessels, both relatively to each other as well as to the ventricles, originate very early in foetal life, and these as well as the unequally-divided vessels are primary defects, and are usually accompanied by many secondary changes. Another malformation occasionally found, involving the beginning portion of the great vessels, is a failure of complete division: the septum truncus communis remains rudimentary, and the blood of the aorta is free to mingle with that in the pulmonary artery. This defect may be accompanied with a rudimentary septum ventriculorum.

7. Ductus Arteriosus Botalli.—This foetal orifice varies greatly in the conditions which are presented; sometimes it is entirely wanting, in others patulous and even in a state of dilatation; in others, again, a short portion is patent (this state is probably comparable to failure to adhere seen in the valve of the foramen ovale or the sieve-like opening in the fossa ovalis; unlike the valve of the foramen, the ductus probably never reopens), or in yet others the ductus is closed in some cases of malformation, and in others of very similar character it remains open. It becomes difficult to explain the varied states of the duct, so dissimilar are they to other defects of development present. In none of the conditions which are presented can the malformations be regarded as of a primary character. Our surprise at certain of its conditions probably must depend on a failure to justly appreciate the primary malformation present, or else on changes in the heart and the circulation coming at a period subsequent to the date of origin of the malformation of the duct itself. When the duct is open at one end and closed at the other, the open part communicates usually with the pulmonary artery, since the closing process commences normally at the aortic extremity: the closure beginning at the pulmonic extremity is occasionally seen in malformations of heart where the blood-current has had a reverse direction through the duct.

The premature closure of the ductus arteriosus Botalli, which is spoken of by some authors, seems to be a rather unfair designation to apply to the condition. In most cases it is in reality an absence of the duct dependent on the defective development of certain of the branchial arches. In other cases the apparent premature closure is due to general uniform narrowing, almost closure, of the pulmonary orifice and vessels; in such cases the lungs are supplied by the enlarged bronchial arteries or other collateral branches. The ductus arteriosus Botalli remains patulous when the pulmonary artery is narrowed or closed; in these cases the blood from the right side of the heart to reach the lungs must pass either through an opening in the septum ventriculorum or through the patent foramen ovale. The duct is generally open in cases of transposition of the main arteries, or even in cases of obstruction of the aortic orifice, or of uniform narrowing of the descending aorta or its main branches. Its usual length and its point of origin from the pulmonary artery or its branches, as well as its junction with the aorta, may vary. Two ducts have been found—one from each pulmonary branch, one of them joining the aorta as usual, the other seeking one of its branches. A distinct duct has been found arising directly from the right ventricle. None of these defects are to be considered as primary malformation, but as the secondary results from alterations of the circulation occasioned by other malformations of the heart or of its great vascular trunks.

Fully bearing in mind the distinction which must be made between primary and secondary defects, and the fact that congenital lesions of the orifices and valves are mostly located on the right side of the heart, let us look at various causes which are capable of producing malformations. In many cases, from the condition of the parts, it is possible to say positively that the alterations are dependent on an inflammatory process commencing in the endo-myocardium at an early period of foetal existence; this is true even after excluding cases in which the inflammatory products present may fairly be considered to be the result of defective development and not its cause. Inflammation was, as has already been shown, long ago pointed out as the cause of these obstructive malformations. Rokitansky (1844) was followed in his views by many, who asserted, probably wrongly, that this condition was the sole cause of the misdirection of development. It was considered that while in very many cases the evidences of the inflammation remained indubitable, in others, through a greater lapse of time, the inflammatory products became less distinct or were wholly removed. Thus, all defects of development may be traced as the results of some obstruction of the pathways of the foetal blood, which, on the one hand, effects the closure of certain vessels or orifices, or on the other hand maintains patent others which normally should be obliterated. It is much easier to trace these causes when they operate during the later periods of development, after the heart and great vessels have assumed the general shape they maintain, than those which operate at the earlier periods of transition. It is plain to us that an obstruction of the pulmonary artery or its branches coming before the end of the third foetal month must, by preventing the flow of blood through it from the right ventricle, maintain an opening of greater or less size in the incomplete septum ventriculorum. It is much less easy—or, in fact, impossible—to be positive about an obstruction or other change which causes the transposition or an unequal division of the great vessels, or which prevents entirely the development of either septum. Nevertheless, we can believe that some obstruction of the foetal circulation causes the former defect as well as the latter, if we may judge of so dark a question by the analogies. In fact, what would present itself as a trifling obstacle in the third or fourth month of foetal life would in the sixth week be an impassable obstruction.

It has been urged against the view that some inflammatory process is the invariable cause of the obstacle, by those who support the development theory, that, as the heart remains in a rudimentary condition, the defects result from a want of formative or plastive activity of the parts. It seems, however, as difficult to account for the want of formative activity which prevents the development of the septum or causes an unequal division of great arterial trunks as to find the traces of an obstruction. Maternal impressions or shocks have doubtless caused many headless foetuses or otherwise misshapen the product of conception during the early months of development. The effect on the foetus from such shocks cannot of course be a direct nervous impression, such as those seen producing local disturbances of nutrition or of formative activity in the adult's own organism, but it is due to disturbances of the placental circulation, by which the blood-current is delayed in the foetal circuit. Such delay may result in a temporary obstruction of the blood in certain foetal vessels. A delay of the blood-current during a few hours in the early period of development of the foetus, when formation is excessively rapid, may result in changes which become permanent. The evidences of such obstruction may fade completely. Osler⁷ has recently urged that it is difficult to suppose an endocarditis limited to the pulmonary valves in an embryo not more than an inch in length, and whose heart could not be above a few millimeters in size. But is it not possible to suppose an endocardial inflammation which affects at the same time, for example, the vascular orifices and the line of the rudimentary septum? The septum may thus be prevented from further development, and the orifice suffer malformation by subsequent contraction. The evidences of the inflammation would greatly lessen as the size of the heart expanded. Cannot inflammation, syphilis, or other communicable disease, from which we know the foetus suffers, be substituted for the unknown "want of formative activity"? In respect to the extent of surface involved in the foetal heart in inflammatory or other morbid processes, can we not suppose that the area exhibiting evidences of disease in the minute heart would be as restricted as in the adult heart? In rheumatic endocarditis of the adult the cause which leads to the inflammation is a general one; the evidences we find of the morbid process, however, are confined to very narrow limits. The reasons for this restriction may be the same.

⁷ Montreal Gen. Hos. Reps., vol. ii.

The simple narrowing of a blood-track where direct evidence is wanting may be explained by the occurrence of a specific morbid process as satisfactorily as by an appeal to lack or excess of formative power. The real difficulty arises in the explanation of cases of transposition of the great vessels. The problem is in every way a most difficult one for solution under any supposition. If it were true that the formation of the pulmonary artery and the aorta was from the start by separate blood-channels, and these distinct vessels suffered a genuine transplantation and became attached to the wrong ventricle, the aorta to the right and the pulmonary to the left ventricle, then undoubtedly we should be compelled to accept the developmental theory as usually expressed. But it is not the case that these vessels are developed in distinct trunks: their development results from the division of a common trunk through an infolding of the walls or the gradual formation of a septum proceeding contemporaneously with the septum of the ventricles, the vessels at the same time making a half turn on their axis. A delay in the formation of either septum may result in the malapposition of the vessels to the ventricles. The septum which is probably delayed in formation is the vascular septum, since it is apparently the growth of this septum that applies the force which results in the axis rotation of the vessels. Are we again to explain the abortive formation of the vascular septum or any portion of the branchial arches by the unknown want of formative power? The want of formative power must have a cause; it does not come spontaneously. Are not inflammatory endarteritis and syphilitic lesions of the blood-channels probable causes of the contraction or obliteration of portions of the branchial arches?

Another question, dark and obscure, requires a short comment. It is commonly accepted, if an abnormal communication (speaking of small openings) exists between the two ventricles, that the septum has been prevented from closing by the blood-current being diverted from its usual course through narrowing of an arterial ostium, and compelled to flow into one or the other ventricle. The patency or the closure of the ventricular septum is held as a criterion of the date of origin of the primary malformation. We know that certain ulcerations of the endo-myocardium may result in forming openings between the two ventricles, but is it not possible that a perforation may be made in the ventricular septum after it has closed by a lesion originating at an arterial ostium of the same character as one that prevented the septum from closing? The muscular tissue of the heart from the third to the sixth foetal month, and even later, is of very soft character. A rapidly-coming closure, or even temporary obstruction, of one or the other great arterial trunks would greatly increase the blood-pressure within the corresponding ventricular cavity. The ventricular septum would become stretched and thin, and might readily be perforated, so delicate is the muscular tissue.

If such a possibility is consummated, it must alter the value which has hitherto been placed on the opening in the ventricular septum as a criterion of the date of origin of the primary lesions of the great vessels which ordinarily are the cause of the patent condition of this partition.

It is to be seen from a review of the recorded cases of malformation of the heart that defects of the arterial outlet of the right ventricle are the primary cause of the largest number of cases. It is impossible to state the proportion of these to those at other orifices or the great vessels, so incomplete are the records and so unlike are the opinions of the reporters. It is but natural that this the more active ventricle of foetal life should exhibit more frequently defects of development, since the left ventricle in adults suffers more commonly in its valvular apparatus during its more active period.

The position at which the defects resulting in obstruction of the blood-current through the pulmonary artery may occur have been mentioned. The degree of the narrowing is of much importance—much more than the seat of the obstruction; but of still greater consequence is the date of origin of the defect of development, since on its occurrence early or late in foetal life depend the condition of the septum ventriculorum and the perfection of secondary compensatory alterations which render the heart capable or incapable of a prolonged extra-uterine life.

Narrowing or closure of the course of the blood passing through the pulmonary artery may be divided into two classes: 1, those cases in which the septum ventriculorum is imperfect to a greater or less degree; and 2, those in which it is fully formed, the separation between the ventricles being complete. The date of their origin corresponds to different periods of the development of the foetus. The earlier the obstruction comes in the normal outlet of the ventricle, the more rudimentary is the ventricular septum. The size of the opening of the septum depends on the degree of narrowing of the pulmonary outlet as well as on the date of origin of the obstruction. If the arteries are transposed in relation to the ventricles, and one of them becomes obstructed, the effect on the septum is the same, although the direction of the current through the opening is reversed. Kussmaul and others have pointed to certain exceptions which may lead to errors. In a congenital opening of the ventricular septum, isolated from other defects, an endocarditis involving the pulmonary orifice may occur subsequent to the time of the usual closure of the septum, or even after birth. It would be difficult to distinguish such a case from one of pulmonary narrowing occurring before the third foetal month. The character of the inflammatory changes and the size of the pulmonary artery beyond the point of narrowing would assist in marking the distinction. It must be remembered, however, that the pulmonary artery is recorded as possessing a large size beyond the seat of narrowing in cases of undoubted congenital origin.

The alteration in the form and size of the right ventricle varies greatly according to the time at which the pulmonary obstruction originates. The ventricle seems to maintain its size, and even to become hypertrophied and dilated, when the pulmonary obstruction occurs before the closure of the septum: if the pulmonary artery is obliterated or exceedingly narrowed at a later period, the ventricle shrivels, because no blood is able to pass, and gradually more and more of the foetal current passes through the foramen ovale to the left side; if, however, the pulmonary defect is but slight, the right ventricle continues its function, becomes hypertrophied, and may dilate. In pulmonary obstruction the right ventricle changes its form somewhat in accordance with the seat of obstruction. Thus the primary obstruction may be in the pulmonary artery or its branches; or in other cases the malformation is found within the cavity of the right ventricle. The last group is spoken of as conus stenosis.

The malformations of the conus of the right ventricle may present themselves under three forms: they all act as constrictions, but alter the shape of the ventricle very variously; their effect on the circulation is practically the same, varying only with the closeness of the constriction. If an inflammatory process occur at the seat of the normal muscular constriction between the sinus and the conus, it may result in fibrous thickening and contraction; thus the normal division of the sinus from the conus becomes exaggerated and permanent. The narrowed portion may continue to exhibit evidences of endocarditis, or these may fade away, leaving a smooth surface. These narrowed parts seem to be especially liable to inflammation at a subsequent period as the bulk of the blood and the force of the circulation increase. Peacock describes a condition of narrowing due to muscular hypertrophy alone. It would seem in these cases that the hypertrophy was, in not a few of the instances, an acquired condition, and not congenital.

These cases present a heart having, as it were, a double or subdivided ventricle, comparable to that of the turtle. The condition has been described by some writers as a supernumerary ventricle. The form and size of the communication between the two portions of the ventricles vary very greatly: in some of the cases due to inflammation the passage merely admits of a large probe, and consists of a firm fibrous ring, or there may be two or more such openings. In constriction by muscular bands the opening is usually a large oval with smooth walls. In these cases the size and the condition of the walls of the so-called supernumerary ventricle present different appearances according to the degree of constriction and the size of the pulmonary opening; it is probable also that the condition of the ventricular septum influences the consecutive alteration in the parts. When the constriction is close and but little blood enters the conus, its walls are thin and flaccid, while in cases of less marked narrowing, provided the pulmonary artery remains nearly normal, the walls of the conus become hypertrophied, in conjunction with a similar development of the other parts of the right ventricle.

In other cases the entire conus may be uniformly narrowed: this change is due almost invariably to inflammatory lesions, and in many instances it is difficult to determine whether the condition is of foetal origin or whether it arose during the early months of extra-uterine life or even at a later period. Its occurrence in conjunction with other malformations would point to its origination during the developmental period. The conus may also present a constriction directly at or just beneath the valvular orifice of the pulmonary artery. This condition is almost invariably combined with some narrowing of the artery itself, and there is so constantly present evidence of inflammation of recent date that it is almost impossible to say whether the defect is not due to a myocarditis originating after the developmental period. With this condition the entire conus usually presents more or less shrinkage or collapse, becoming greater as the constriction at the orifice is more marked. This collapse of the conus is to be looked upon as secondary to the primary defect at the orifice.

Closure or narrowing of the pulmonary artery trunk may be traced to many conditions acting at several different points of the course of the blood. Nearly all these conditions are caused by inflammatory lesions which result in contractions of the arterial walls. In fact, pulmonary artery defects not dependent on inflammatory changes are very obscure and difficult of explanation. In adult life we know of only two conditions which lead to obliterations of vessels; first, inflammation of the lining membrane (endarteritis); and second, stoppage of the blood-current, usually through pressure directly applied to the vascular trunk. The clots of blood which occupy the vessels form both in advance and beyond the point of pressure; hence we can look for obstruction, causing closure of the pulmonary artery, at either extremity of the blood-course. Thus, we may think of a primary conus obstruction which may secondarily have the effect of reducing the size of the pulmonary artery, but it is never obliterated through this means; nearly always some blood passes in this direction, and blood also enters the pulmonary artery from the ductus arteriosus Botalli: both conditions necessarily tend to keep the artery from complete collapse; moreover, the artery, even in cases of very narrow conus, may remain of its usual size. The same effect may be produced by narrowing of the tricuspid orifice. This condition is a very rare one, and never could lead to complete closure of the pulmonary artery unless this orifice were entirely obliterated and the septum of the ventricles remained closed. Peacock speaks of premature occlusion of the ductus arteriosus Botalli as one of the causes of narrowing of the pulmonary artery. The obliteration of this portion of the branchial arches, by preventing the blood flowing in its usual course to the descending aorta, he thinks results in narrowing the calibre of the pulmonary artery. May not the condition be equally well interpreted in a different manner? May not it be that the obstruction of the artery was the cause of collapse of the ductus? One would think it possible, if an obstruction arose in the ductus arteriosus Botalli, for the blood-current in the pulmonary artery to maintain another branchial arch patulous for its accommodation, or, failing this, to dilate the pulmonary branches and thence return to the left side of the heart. In rare cases the pulmonary artery has been found deficient in size when the lungs are malformed, either by reduction in their size as a whole or by the absence of one or more lobes. Such a cause has very little opportunity of acting with much force on the pulmonary artery during foetal life. This cause and all the others in this group are to be looked upon as secondary in their effects.

In primary defects of the pulmonary artery trunk the vast majority afford indubitable evidences of an original inflammatory causation; others are due just as positively to a defective evolution of this vessel from the common arterial trunk. Instances are on record of the complete closure of the pulmonary artery and its conversion into a ligamentous cord: these cases are very rare. In a somewhat larger number a pretty uniform narrowing, sometimes to an extreme degree, and often exhibiting thickened walls, is found. It is much more frequent to see the obstruction of the artery, due to inflammatory changes, at its valvular orifice.

Peacock describes the narrowing at the pulmonary orifice in many cases to be due to disease of the pulmonary valves, whereby the number of cusps are reduced in number, or to a membrane stretched across with small openings in its central portion; or the obstruction may consist of a duplicature of the lining of the vessels, or even to bands of muscular fibres surrounding the orifice. Two valves of unequal size may be found at the orifice, giving evidence that the larger one has been formed by the adhesion of two of the normal cusps; the membranous obstruction is probably due to the union more or less complete of the three cusps. The curtains thus formed protrude into the course of the artery and form a deep circular sinus between the valves and the walls of the vessel. The opening between these adherent valves varies from a transverse slit to a tubular or barrel-shaped orifice—a tube within a tube. These diseased valves are thickened, very firm, fibrous, or even calcified. In other cases the obstruction consists of abundant warty elevations, so numerous that they are equally effective in preventing the passage of blood as the united valves. The size of the opening is sometimes extremely reduced, measuring only five millimeters in diameter. The pulmonary artery is most generally less in size than normal, but never becomes reduced to the same extent as its orifice, unless it has likewise suffered from inflammatory disease; otherwise its walls remain thin, resembling the venæ cavæ.

In addition to disease within the calibre of the vessel, Meyer, who strongly advocated the inflammatory cause for all these defects, pointed to pericarditis, occurring at the origin of the pulmonary artery and compressing the vessel, as a rare method of causation.

In a very large majority of the cases of pulmonary narrowing on record the septum ventriculorum is found to be more or less defective. In accordance with the usual principles, this defect of the septum, in conjunction with narrowing of the pulmonary artery, is held to indicate that the obstruction of the artery dates from a period of development anterior to the closure of the septum. This view was advanced by Hunter in 1783. But Peacock gives an account of many cases of pulmonary narrowing, combined with open septum ventriculorum, in which the obstruction was caused by adhesion of the pulmonary valves. It is, however, a fact that the development of the valvular apparatus is not effected until after the septum of the ventricles is completed. How, then, can we suppose valves to adhere so as to obstruct the pulmonary artery and prevent the closure of the septum when in reality the valves themselves have not developed? Does it not seem possible that in some rare cases the opening found in the septum ventriculorum is in reality a reopening? Another case is on record of open septum ventriculorum and narrowing of the pulmonary orifice in a child born of a mother who suffered a prolonged fright during the fifth month of utero-gestation. Strong mental impressions are accounted causes of malformation of the foetus, and in this case the fright, if it was the origin of the defective development of the septum, came more than two months too late.

In cases of pulmonary narrowing with open septum the aorta communicates freely with the right ventricle, or appears to arise from both ventricles, or more rarely from the right cavity alone (the deficient pulmonary artery remaining in its usual position). Many opinions have been held as to which one of the three defects is primary. Hunter's conclusion has most generally prevailed. The obstruction of the course of the pulmonary artery is looked upon as the primary defect. From the obstruction the right ventricle becomes distended, and the opening of the septum is due to the blood-pressure, which prevents the final closure. The blood-pressure also alters the direction of the septum and pushes it farther to the right. Thus the septum comes to stand directly under the aortic orifice, or by a further deviation to the left side brings that orifice wholly within the right cavity. In these simple cases the origin of the aorta from the right ventricle is not a real but merely an apparent transposition or transplantation of this vessel; the aorta has not been moved, but only the septum has been moved under its orifice, and the right ventricle has consequently become more extensive. In other cases the aorta seems to move more toward the right side, usually coming also more to the front, and in other cases there is an actual transposition of these vessels. The method of this transposition will be further described.

Meckel's original theory for open septum and narrowed pulmonary artery was that the defect was primarily in the septum of the ventricles, due to a want of formative energy, and the pulmonary artery closed itself, as do other arteries, from want of use. Meyer showed that a defect of the septum was incapable of causing narrowing of the pulmonary artery, since the exit of blood is easier through the artery, from the form of the right ventricle, than through the open septum; the passage of the blood from right to left is opposed by the blood-mass in the left cavity. Heine also thought the pulmonary-artery narrowing was a secondary defect, but did not think the opening of the septum caused the narrowing. He considered the primary malformation to be a deviation of the septum to the left. The deviation of the partition before its closure brought the aorta within the left cavity, and furnished a free exit for the blood from this chamber shorter and more convenient than through the pulmonary and the ductus arteriosus Botalli to the descending aorta; the pulmonary artery collapsed for want of use, similarly to other foetal blood-courses. Hence, Heine considered that in all cases of open septum and apparent transposition of the aorta which exhibited no evidences of inflammation as a conjectural cause of narrowing or closure of the pulmonary artery the explanation was to be found in a primary deviation of the septum ventriculorum.

The difficulty in Heine's theory lies in showing the mechanism of a deviation of the septum without a primary obstruction of the flow of blood through the pulmonary artery. The hypertrophy of the right ventricle which Heine proposed as an explanation is almost certainly a secondary effect of the obstruction, and therefore cannot be supposed to originate a deviation of the septum; it is doubtful if hypertrophy can be considered as a cause of increased blood-pressure within the cavity of a ventricle under any circumstances, and certainly not as exercising pressure in a direction to cause the supposed deviation of the septum. An open septum without obstruction of the pulmonary orifice, which rarely occurs, does not produce hypertrophy of the right chamber.

The explanation of cases of open septum with obstruction of the pulmonary artery seems entirely satisfactory by Hunter's theory, or by what Kussmaul has named the engorgement theory. But when there is a real transposition of the arteries, the pulmonary placed farther to the left and behind and coming from the left cavity, the aorta in front and to the right and arising from the right or pulmonary chamber, thus changing their relative positions and their orifices exchanging ventricles, the difficulty of explanation becomes great, and the cause of the abnormal relations of the vessels cannot be traced to a simple deviation of the septum ventriculorum.

For the explanation of these cases of complete transposition of the vessels, as well as their transplantation relatively to the ventricles, Rokitansky has traced respectively the development of the two arterial trunks from the common trunk and of the septum ventriculorum. He considers that the partitioning of the arterial trunks is the governing factor in their formation, and that the ventricular septum is arranged in conformity with the septum of arterial trunks. In tracing the development of the circulatory apparatus in man there seems to be no doubt that the heart develops exactly like that of other vertebrates.

The very first rudiment of the heart is a spindle-shaped thickening of the intestinal fibrous layer of the fore part of the alimentary canal. This spindle-shaped formation then becomes a hollow pouch, and separates from the intestinal layer and lies free in the cardiac cavity. The earliest condition yet seen in the human being is that from an embryo of about two weeks (Coste), in which the viscus appeared as a simple tube in the shape of a letter S—the hollow rounded pouch having slightly elongated and bent to this form, and simultaneously turned spirally on an imaginary axis, so that the posterior part of the tube rested on the dorsal surface of the anterior part. The yelk-veins connect at its posterior part, while the arteries form a continuation of its anterior extremity. The spiral turning and curving increase, and simultaneously two shallow indentations appear in the twisted pouch, transversely to its long axis, looking like kinks in a flexible tube. These indentations mark the outline of the three primitive portions of the central organ—viz. the first, with which the veins communicate, represents the future auricles; the next, the ventricles; the third portion, the common arterial trunk (aortic bulb or truncus arteriosus communis). Early in development the first section is the largest, but by the time the S is formed the middle or ventricular portion exceeds in size the auricles and their appendages. So far, the central organ remains a continuous tube, indented transversely in its course at the points which mark its future division; the blood moves through it as through a coiled tube, entering by the veins and passing out by the aortic bulb to the vascular or branchial arches; the venous entrance is posterior, the arterial exit is anterior and is directed toward the future aortic arch. This is the condition at the end of the second week. The future auricles and ventricles now form a common cavity; the indentation between them, called the auricular canal, represents the future auriculo-ventricular orifice. The future fibrous ring forming this orifice is the first to be developed of all the permanent structures of the heart; its infolding to form the two auriculo-ventricular orifices comes early, but at a later date than here spoken of. Its exact method of development is not clearly described.

Between the second and fourth weeks is exhibited an indication of the future most important step in development; this process does not really step forth until the fourth week, although superficial traces of a furrow antedate this time. This step is the division of three sections of the tube into opposite halves, a right or venous, a left or arterial half. This division results in the formation of the future septa between the auricles and between the ventricles, and separates the common arterial trunk (aortic bulb) into the future aorta and pulmonary artery. This partition is spoken of as longitudinal; but it will be seen, if the real lines of growth of the future auricular and ventricular septa are carefully regarded, that the indentations which mark their site are also transverse, as were the primitive ones for division of the auricles from the ventricles. The proximal end of the tube comes in contact with the distal portion by a further bending movement, so that these two ends go to make the left half of the heart; and the middle portion of tube, composed partly of auricle and partly of ventricle, forms the right half of the heart. This secondary indentation, commonly spoken of as longitudinal, is in reality transverse, although, from the more markedly bent condition of the tube which has come about, it does not advance in the same plane as the primitive indentation of the tube. The mechanism of the division of the aortic bulb will be described later.

This secondary indentation, which finally results in the formation of the auricular and ventricular septa, appears earlier in the ventricular cavity, about the fourth week, and later in the auricles, about the eighth week. By about the twelfth week the process of formation for the muscular partitions is completed; the septum ventriculorum normally is gradually built up, and by this time has joined itself, at the base of the heart, to the septum forming itself in the arterial bulb; thus the right and left ventricles are finally separated. The septum in the auricles is also finished in its muscular part, mostly built up from the base and posteriorly toward the roof of the cavity, leaving, however, the foramen to be closed by the membrane some days after birth.

The foetal heart from the fourth week onward becomes more and more rounded in outline, and finally more or less rectangular. The auricular appendages become conspicuous and overhang the ventricles. The future left ventricle appears larger than the right, and the former projects notably leftward and downward. The aortic bulb or common trunk appears to arise wholly from the right ventricle, although the vessel communicates with both cavities, since at this period the cavities are undivided. The furrow which marks the line of the future septum ventriculorum runs to the left of the root of the common trunk; and until at least as late as the sixth week this trunk appears from the exterior to be in connection only with the future right ventricle.

As early as the sixth week, possibly earlier, a distinct furrow is seen on both sides of the common trunk running longitudinally from its root at the ventricle to its first branch (branchial arch). This indentation does not traverse directly to the ventricular furrow; in fact, at this period the ventricular furrow is not conspicuous at the origin of the trunk toward the base of the heart, the septum within not having risen as yet to the base of the ventricles. During the formation of this furrow the common trunk continues its slow partial rotation on its axis; the rotation of the other parts of the cardiac tube has ceased; the segments of the tube have come to a standstill—become, as it were, fixed and adherent to each other, the proximal to the distal end, the anterior surface to the posterior, through the previous bending of the tube on itself.

Within the common trunk Rokitansky has described the changes, as seen in cross-sections, which result in its division into a permanent aorta and pulmonary artery, and also the adaptation of the septum arteriosus trunci to the septum ventriculorum. He says that at an earlier period than here described for the external furrow appearing, on the inner surface of the truncus arteriosus communis (aortic bulb), to its left side and somewhat posteriorly, above the starting-point of the anterior limb of the septum ventriculorum, a little swelling appears, which grows toward the right and slightly forward, so that the common trunk is divided into an anterior rather left-hand, and a posterior right portion, respectively the pulmonary artery and aorta. The growth does not pass in a straight line through the lumen of the common trunk, but so that the forming septum makes a concavity posteriorly toward the aorta, and a convexity anteriorly toward the pulmonary; thus, on cross-section the aorta has the outline of the gibbous moon—the pulmonary, fitting into it, separated by the septum, of a new moon. The septum ventriculorum, as seen starting at the base of the ventricles from the fibrous ring of the auriculo-ventricular orifice (having already been built upward from the future apex of the heart), originates at a point on the posterior wall of the common ventricular cavity in exact correspondence with the starting-point of the little swelling on the inner surface of the common arterial trunk. The two septa are thus formed in apposition. The septum ventriculorum, in advancing forward to meet the other limb of the septum forming on the opposite wall of the ventricular cavity, follows the septum trunci arteriosus communis, surrounds the posterior vessel (the aorta) to its front, then passes around it to its right; the pulmonary is on the other side of the septum; the portion of the septum ventriculorum between the orifices of the vessels is the pars membranacea of the septum. The anterior portion of the septum ventriculorum forms one wall of the arterial conus of the right ventricle. Thus it happens that by the eighth week the common trunk is divided into aorta and pulmonary artery; the structure of the septum ventriculorum is so far advanced that these vascular trunks are connected with the proper ventricles, but the septum ventriculorum does not close completely until about the twelfth week.

In explaining the occurrence of a transposition of the arterial trunks in accordance with the facts of their normal development, Rokitansky says, if the septum trunci, starting from the usual point of the little swelling on the inner surface of the common trunk, turns abnormally with its concavity forward (instead of backward as normally), and thus passes through the trunk, there will be established an anterior left aorta and a posterior right pulmonary, because the septum ventriculorum in its growth conforms to the direction of the septum trunci. Thus, another than the usual portion of the common trunk is partitioned off and placed in communication with the respective ventricles. This furnishes us with examples of transposition of the arterial trunks relatively to each other, but not transposed in relation to the ventricle into which they are implanted. The great majority of specimens of this sort with which we are acquainted—and Rokitansky knew no others—show an open septum. They are usually spoken of, therefore, as instances of "both vessels arising from the same ventricle (the right usually)," or of "aorta communicating with both ventricles, the pulmonary artery normally placed." Rokitansky assigns no reason for this deviation in the line of growth of the septum trunci across the lumen of the common trunk; in fact, he never examined a malformed heart during this stage of development. The deviation of the septum trunci, the primitive factor in this malformation—since to it the septum ventriculorum conforms its development—he accounts for by chance (deviation of formative energy). It seems much more probable, as it is always the pulmonary artery which must be reduced in size when the concavity of the septum trunci presents anteriorly (the aorta occupies the smaller area when the concavity of the septum is posterior), that the deviation of the septum trunci is due to some one of the many conditions (endo-myocarditis) which have already been pointed out as the cause of pulmonary-artery narrowing or closure; hence, another malformation of the heart can be thus traced to pulmonary obstruction, the evident cause of so many other defects.

For examples of transposition of the vessels, both relatively to each other and to the ventricles, with complete closure of the septum ventriculorum, Rokitansky also gives a satisfactory explanation. It is important to note the distinction between cases of closed and open septum. Transposition of the vessels with open septum are, as already shown, doubtful instances of transposition from one ventricle to the other, although the vessels may be transposed in relation to each other; furthermore, the mechanism which explains relative transposition of the vessels does not explain the implantation of the vessels into the improper ventricle. His explanation is that the starting-point of the little swelling from which the septum trunci forms is shifted to a point farther forward on the inner circumference of the common trunk, and at the same time has its concavity anteriorly, and as in the previous case decreasing also the area of the pulmonary artery; and thus the aorta comes more forward and to the right, and the pulmonary artery passes more to the left and backward. The septum ventriculorum, in conforming itself to the abnormal starting-point and direction of the septum trunci, must consequently pass across the common ventricular cavity in such direction that the aorta comes in connection with the pulmonary side of the heart, and the pulmonary artery with the systemic heart. Consequently, Rokitansky traces both the relative and the actual transposition of the arterial trunks to the deviation either of the direction or of the starting-point of the septum trunci. The deviation of the position of the little swelling on the inner surface of the common trunk, which Rokitansky supposes, is probably not an actual transference or misplacement of this point of formative energy, but in reality a failure of the common trunk (aortic bulb) to continue its axis-rotation, as it normally does, after the other portions have become fixed. This premature cessation of the rotation of the common trunk would leave the starting-point of the septum trunci in a more anterior position than normal, since the trunk rotates normally in a direction to bring its left side, on which the starting-point of the septum trunci is situated, more posteriorly. A pericardial inflammatory adhesion, such as Meyer pointed out for certain cases of pulmonary artery obstruction, would fix the common trunk, prevent its proper rotation, and at the same time narrow the pulmonary orifice in certain instances. In other cases, in which the pulmonary artery is found of normal size, the septum trunci may be supposed to divide the vessel in the usual direction (concavity posteriorly as normal), whilst the septum trunci commenced to grow from an abnormal position, more anteriorly and to the left than normal (through failure of rotation); hence, as the septum ventriculorum conforms to its growth, the vessels become connected with the improper ventricle; the pulmonary, however, is not found permanently narrowed, and the septum ventriculorum is completely closed. Here the cause is a failure of the common trunk to rotate on its axis, probably from an external adhesion of its periphery.

Malformations affecting primarily the Right Side of the Heart.

In classifying defects in the course of the pulmonary artery we come to—

1. Closure or narrowing of the artery, with perfect ventricular septum.

Congenital obstruction of the pulmonary artery, with closed septum, although more rare than with open septum, is nevertheless a frequent defect. Unfortunately, it is very often impossible to distinguish with certainty whether the stenosis is essentially congenital or is acquired after birth. Complete closure is the least difficult to distinguish, because this defect very soon causes death; the prognosis in a merely narrowed orifice is much more favorable. The duration of life in complete closure never extends beyond a full year, while in undoubted congenital narrowing the age of sixty-five years has been attained.

From this atresia the most striking consequence is a reduction of size of the right ventricle, increasing almost to closure. This result is so common that Peacock thought it was the law that in atresia the right ventricle reduced itself to closure, while in stenosis it dilated and became hypertrophied. This is not the law, but only a rule of very common occurrence. Instances of eccentric and concentric hypertrophy are found among the records of these cases. Great reduction of the right ventricle results probably only when the obstruction comes very soon after the completion of the septum ventriculorum—thus at a time when the ventricle is yet very small. The wasting of the right ventricle can reach a very high degree, and when it becomes very great the tricuspid orifice is also defective. The foramen ovale and the ductus arteriosus Botalli are, in complete closure, usually found open. The obstruction may come in the conus or at the valvular orifice, or the artery is found converted into a cord.

In seven cases the duration of life varied from four days to nine months.

When the stenosis does not reach a high grade, positive clinical signs are often wanting for the determination of its existence, and the difficulty becomes greater as the age of the person advances.

Clinically, we find congenital blueness with palpitation, dyspnoea, together with the physical signs of pulmonary stenosis; these symptoms, however, may make their first appearance only on the advent of some acute disease. Sometimes they come in the first month or the first year of life, or even much later. If abundant congenital compensatory changes are present, the symptoms may be postponed until further compensatory alterations become impossible; or at the narrowed orifice the development of a fresh endocarditis may determine the occurrence of symptoms. The mere increase of the body and of the mass of the blood may alter the relations of the circulation, and this disproportion may show itself with suddenness. Febrile conditions may also suddenly disorder the circulation.

The compensatory alterations which commonly are held to indicate a congenital origin of stenosis of the pulmonary artery are patulousness of the auricular septum and of the ductus arteriosus Botalli. When both of these remain open there cannot be much doubt that the date of origin is from the foetal state or in the first weeks of life. If only one of the foetal passages remains open, the ductus gives a greater surety of a foetal date than the foramen ovale. The closure of both foetal passages does not exclude a congenital origin if the obstruction of the pulmonary orifice is moderate. The patulousness of both foetal passages indicates that the defect arose at least shortly after birth, because these openings close within four or five weeks of this event. The foramen ovale alone open indicates very little with certainty, as it is so often found with one or more small openings without any probable cause. Bézot found it partially unprotected in 44 cases out of 155; Klob, 224 in 500; Wallmann, 130 in 300. Rokitansky has indicated that a strong blood-pressure not unfrequently may press the fibrous valve of the foramen strongly toward one auricle or the other, and thus lead to its atrophy in part, forming larger or smaller openings of communication between the two cavities. In doubtful cases of stenosis of the pulmonary artery such small openings are not signs of much value in determining the congenital origin of the stenosis. Unless there is a marked defect in the septum atriorum, the congenital origin of the pulmonary atresia or stenosis cannot be predicated on this ground.

Patency of the ductus arteriosus Botalli has been very rarely observed as a primary malformation. A coincidence of this as primary defect with post-natal stenosis of the pulmonary artery must necessarily be extremely rare. In persistence of the ductus art. Botalli the current passes from the aorta toward the pulmonary artery; the obstruction of the pulmonary artery conditions a dilatation with hypertrophy of the right ventricle. Reopening of the closed ductus is impossible.

The condition of the pulmonary valves as well as the diameter of the pulmonary artery itself and its branches often afford valuable points for the determination of the congenital origin of stenosis of this orifice. The greater the narrowing, or the more extreme the thinning of the wall, the earlier the coming of the obstruction.

Morgagni reported the first case of stenosis of the pulmonary orifice—in fact, the first case of congenital malformation of the heart—in a girl aged sixteen. He recognized the relationship of the open foramen ovale and the dilatation of the right ventricle as mechanical effects of the pulmonary stenosis.

2. Obstruction of the conus arteriosus dexter, with open ventricular septum.

A. The separation of the conus in the form of a so-called supernumerary third ventricle has been reported by Peacock in ten cases, and ten others have been added by Kussmaul from various sources. The degree of separation varies very greatly in individual cases: in some it is so slight that the designation becomes doubtful, while in others it is so great that the word stricture might with propriety be employed. In two cases a goosequill-sized opening existed between the sinus of the right ventricle and the conus; in others the communication between the two was multiple. The size of the supernumerary ventricle varies greatly; in one case of a girl of twelve years it would only contain a hazelnut.

In most of the cases the partitioning probably commences by hypertrophy of the muscular bands which are more or less marked in normal hearts in this situation: to this, as the result of endo-myocarditis, is added cicatricial contraction of the inflammatory products, whereby the original partitioning becomes greatly increased. The preponderating frequency of the seat of the stenosis directly at the transition of the conus to the sinus increases the likelihood of this explanation of its causation.

Alteration of the valves of the pulmonary artery, probably of foetal inflammatory origin, is of very frequent occurrence with supernumerary ventricle and conus stenosis; sometimes only two cusps are found, though four cusps have been noted; they may be absent or be replaced by a ring mass formed from their union. Normal valves have been observed unaltered by inflammatory changes. The conus appears always to suffer diminution, and the pulmonary artery is found more or less narrowed according to the degree of obstruction. The sinus of the ventricle is dilated and its walls hypertrophied. The aorta, mostly widened, springs in all cases from both the ventricles, unless wholly from the right one. The foramen ovale is generally more or less widely open, although it has been found closed; the ductus art. Botalli is mostly closed. The duration of life may be long; Kussmaul reports the oldest case at thirty-eight years.

B. Of primary uniform narrowing or shrinkage of the right conus art. dext. Kussmaul reports eight cases from various sources. The conus was shortened, and formed a ring-shaped fissure, gradually reduced in size toward the orifice of the pulmonary artery. The pulmonary valves were variously changed, mostly by union of one or more of the cusps, though sometimes remaining normal in shape, though very delicate. The pulmonary artery was generally narrowed to about the width of the calibre of the conus itself, unless further change came to it from its special involvement by endarteritis.

In all cases the aorta arose from both ventricles. The right side of heart was dilated, and the right ventricular wall hypertrophied. The foramen ovale remained open. The ductus arteriosus Botalli has been found absent or closed, and the collateral circulation effected by anomalous communications, oftentimes duplicate or manifold; in most cases the ductus remains open. The oldest patient in which this form of heart has been found was twenty-five years.

C. Ring-formed narrowing of the conus, due to a muscular band. Peacock reports this defect from a girl æt. nineteen, cyanotic from birth; the constriction was situated at the bases of the valves, and was formed by a muscular band covered by fibrous tissue, and the edges of the opening were studded with warty vegetations. The pulmonary valves were two in number, probably resulting from fusion of two of the cusps; were thickened and opaque, but smooth. The index finger could be passed between the valves. The artery was of small size, but much wider than the constriction. The aorta was dilated, and arose from both ventricles through a perforation of the septum ventriculorum. The foramen ovale was closed. The ductus art. Botalli gave free passage to a crowquill. The right side of heart showed dilatation and hypertrophy of both its cavities, and the tricuspid valve was thickened and had vegetations on its auricular aspect.

3. Simple stenosis and atresia of the pulmonary artery, with open septum ventriculorum.

This class includes malformations, with stenosis or atresia of the pulmonary artery, in which the defects occur before the completion of the ventricular septum, as the result of engorgement already described, but in which no other primary congenital defect exists; thus the separation of the pulmonary artery from the truncus arteriosus communis is completed; the auricles and ventricles are marked out by their septa, though not completely divided; the position of the aorta in relation to the pulmonary artery is either normal or more to its right; and there are no primary defects of any consequence in the other orifices of the heart. The simple stenosis or atresia of the pulmonary artery as thus defined is by far the most frequent malformation of the heart. Kussmaul has found about 90 described; among these are 26 cases of atresia.

As a rule, in partial obstruction the entire length of the artery, as far as the bifurcation, shows narrowing, but the greatest narrowing exists at the orifice of the pulmonary artery; only rarely are the orifice and the tube equally narrowed. Exceptionally, the tube has been found narrower just without the orifice, and later resumed its normal circumference. The walls are very often thin, like those of veins, and at times the vessel is shrunken. The valves are variously altered, often to a greater or less degree united, thickened, and opaque.

In complete closure two different conditions are seen; in some the artery itself to its bifurcation changes to a firm cord or thread; in others the tube is more or less narrowed and the orifice alone is closed.

As a rule, in stenosis and atresia of the pulmonary artery the conus is only moderately narrowed and its walls hypertrophied, while the sinus of the right ventricle is dilated and hypertrophied. The right auricle is dilated and hypertrophied. The tricuspid leaflets are clouded and thickened. The left ventricle is commonly small, and the wall not thicker than the dilated right ventricle. Sometimes the aortic and mitral valves suffer alterations of an inflammatory sort, probably of foetal origin. The shape and position of the heart are changed, but the size, as a whole, may not be much altered. The aorta may be widened, often to double the normal size. As to the origin of the aorta, it is often difficult to speak with certainty; its relative position to the pulmonary artery and to the body and axis of the heart is, as a rule, unchanged. Whether it is to be described as arising from one or both ventricles, or from the right one alone, depends on the posture which the septum ventriculorum assumes beneath its orifice. As a matter of fact, this relationship makes little difference to the flow of blood from the right ventricle, whose normal orifice is obstructed; provided the septal opening is sufficient, the flow of blood is secured and the hindrance to the circulation precluded. The opening in the septum ventriculorum may be only at the membranous portion, or it may also involve the adjacent muscular septum; the defect may be round or triangular, with its apex above and with smooth margins.

The foramen ovale has been found open in 39 cases out of 53. Its condition in this respect shows very great proportional variation in the different collections of cases. The open or closed condition of the foramen does not seem to depend on the degree of stenosis of the pulmonary artery itself. It depends, probably, more on the freedom of escape for the blood from both the ventricles through the aorta—probably also on the condition of the ductus arteriosus Botalli. The foramen ovale and ductus art. Bot. have been found closed much more frequently in stenosis than in atresia of the pulmonary artery, and the ductus is deficient or absent oftener in stenosis than in atresia. This absence of the ductus occurs in 13 per cent. of the cases, and tends to support Peacock's theory that narrowing of the pulmonary artery is the consequence of the defective development of that branchial arch out of which the ductus art. Botalli is formed.

It is of great interest to note the collateral circulation by which blood reaches the lungs when the pulmonary artery is closed. When the ductus arteriosus is open, the blood passes from the aorta into the ductus and the branches of the pulmonary artery become branches from it. When the ductus arteriosus is closed or very narrow, the bronchial arteries become the means of supply for the lungs, and through them the blood passes to be aërated. Branches from the coronary arteries have been found supplying a partial channel for the blood to the lungs, as well as the oesophageal, pericardial, internal mammary, and intercostal arteries.

The duration of life is often very considerable. Thirty-seven years have been attained.

4. Combined Stenosis and Atresia of the Pulmonary Artery.—Under this division are arranged other primary defects of the heart, which are found combined with stenosis and atresia of the pulmonary artery. It is very striking how frequently this artery is narrowed or closed in defects of the heart which date from the early period of foetal life, before the division of the truncus art. comm. and of the ventricles has occurred. It is only very rarely that defects from this early period show a normal width in this vessel; in the great majority it is narrowed or closed. The aorta is rarely affected in this manner. Changes in the aorta may come also, but a complete failure or great narrowness of this circulation is so difficult to overcome by a collateral circulation—more difficult than the pulmonary circulation—that life must cease in the foetus, or at least the conditions are incompatible with extra-uterine existence.

A. Combination with partial persistence of the truncus arteriosus communis. The defects coming under this head show usually very great deficiency of the organ and its great vessels, although the heart itself in rare instances shows the proper arrangement of the cavities and their valves. The persistence of the truncus art. comm. may be complete or partial; the defect consists in the total absence or arrest of growth of the septum of the truncus, which partitions it into two portions. Normally, the two septa grow simultaneously and meet at the base of the heart. In cases of persistence of the truncus art. comm. the upper septum fails to develop. In incomplete division of the truncus the pulmonary artery suffers more than the aorta, and the former is always narrower than its fellow-vessel. This difference varies greatly. The valves of the pulmonary artery often fail entirely, and the ductus art. Botalli is many times absent.