Volume 1 — GENERAL DISEASES. (continued 22)

As for the time of year, we quote the following: "Thus, according to the census statistics, most deaths occur in the spring, there being a rise up to the middle of May. From the middle of May the number lessens largely until August, when a rise occurs and continues until October, when a decline sets in and continues until December, when a rise begins and goes on increasing until the middle of May. This rise in mortality from August to October is attributed to the wear and tear of a hot summer and the intestinal troubles then so prevalent."

The mortality statistics of this disease are uncertain. It is fatal in its complications or by inducing a debilitated condition which invites degenerative processes. The severity of the symptoms is no guide for prognosis as far as uncomplicated cases are concerned, and there is no doubt but that at present we are able to greatly reduce the mortality-rate by care and medical treatment, as well as to shorten the attack. Sporadic cases are apt to be neglected until they become complicated. When the disease occurs in epidemic form, measles is often prevalent simultaneously, and in consequence children who become affected by both diseases have a greater tendency, from debility, to become the victims of those affections of the respiratory organs which are such frequent and fatal complications of both maladies.

Instead of surprise at the mortality of this affection, the marvel is that so large a percentage of recoveries take place, when we consider that we are dealing with a disease whose lesion is a catarrh of the air-passages which seldom lasts less than two months, with a tendency to involve the lungs in one way or another, and then witness the carelessness with which, among the lower classes, the child is often treated—exposed to all weathers, under-clothed, under-fed, and probably allowed to pass through the whole attack without medical treatment. Taking this into consideration, the probability is that the mortality of this disease could be reduced to a very small figure by careful management, even if the investigations of those now seeking the microbe of pertussis do not lead to any plan, in accordance with Pasteur's teachings, which will still further lessen the gravity of the disease. Until then, we can but insist upon a rigid quarantine of schools, a registration of all cases, and the seclusion of them, as we have done to-day in the case of variola and scarlatina.

MORBID ANATOMY.—Although whooping cough is a serious disease, the cause of death is generally found to be dependent upon its complications, and there is no lesion at all characteristic of it. The chief complications and sequelæ are—bronchitis, which may become capillary; lobular collapse, which, according to Alderson,⁵ is frequently found; emphysema, usually marginal, probably due, as suggested by Jenner, to violent expiratory exertions; rupture of air-vesicles, with subcutaneous emphysema; catarrhal pneumonia, pleurisy, phthisis, acute tuberculosis, croup, cerebral apoplexy, meningitis, etc. As any of these complications, and others which may arise from debility, may be the cause of death, independent of the action of the specific poison itself, it is usual to divide the post-mortem appearances into those that are the result of the extension of the catarrh itself and those produced by the interference with the circulation and with nutrition from mechanical violence. Of the former, the usual causes of death are pneumonia, gastritis and enteritis. Of the latter, we have thrombosis of the cerebral sinuses, hemorrhages, emphysema, and exhaustion following constant vomiting.

⁵ Medico-Chir. Trans., pp. 90, 91, 1830.

Tubercular disease of the lungs or of the brain is apt to be a cause of death. Convulsions carried off 5 of the 12 fatal cases reported out of 208 by Meigs and Pepper. This may be due to congestion of the brain, especially in teething children. Spasm of the glottis with sudden death is occasionally found. In such cases there is found intense congestion of the brain, also of the liver and kidneys, and at times of the mucous membrane of the stomach and intestines, as well as of that of the respiratory tract.

In all cases, especially at the teething age, sudden death may occur because effusion into the ventricles of the brain or the formation of heart-clot has taken place. It is important to know this, that active treatment applied early enough may save the patient.

PROPHYLAXIS.—Should the interesting and seemingly conclusive statements of Dolan and the microscopic investigations of Carl Bruger⁶ receive the endorsement of future workers, the subject of prophylaxis will assume a degree of importance which hitherto it has only maintained with the medical profession. No one has doubted that the disease was contagious, and yet there is no affection which has attached to it a corresponding fatality that is so carelessly dealt with as pertussis.

⁶ Bruger of Bonn, in the Berliner klinische Wochen., describes at length the special micro-organisms of pertussis. They appear as small elongated elliptical bodies of unequal length, the smallest being double as long as broad. High powers show subdivisions in the largest specimens. They are generally isolated, but may appear in groups. They bear some resemblance to Leptothrix buccalis, the spores of which are often found in whooping-cough sputa. Occasionally the bacillus is seen inside the mucous corpuscle in the sputum. They stain in the usual way, fuschin and methyl violet. This bacillus is not found in any other kind of sputum, is very abundant in pertussis, and increases in direct proportion to the severity of the disease.

Within the past few days we have heard on two occasions in crowded railway-cars the characteristic paroxysm of the third stage of the disease, and yet people will endeavor to convince themselves that unless contact with the child takes place the danger is little.

The atmosphere in school-rooms, railway-cars, and places of amusement which are badly ventilated, is an excellent medium for the propagation of the contagious matter, and many extraordinary cases are on record of momentary exposure being sufficient to contract the disease. Believing that the contagium or virus resides in the mucus and air thrown off by the child, and also in the vomited matters, which contain a large amount of ropy mucus, and also that it gains entrance by means of the respiratory organs, protection from contagion divides itself as follows: thorough disinfection of the exhaled air, of the mucus remaining within the bronchial tubes and air-passages, and of the clothing, together with exposure to fresh air and thorough cleansing of all furniture and household utensils, including cups, silverware, and toys, used by the child. Oxygen is said to have this effect, and thorough, constant ventilation, with the breathing of fresh air by the child, the thorough washing of its surface, and disinfection of its clothing, are the first indications; while the impregnation of the atmosphere with the spray of well-known germicides by means of the steam or other atomizer and the frequent inhalation of such materials by the patient are no less important. Every case of whooping cough should be compelled to use two or three times daily the spray impregnated with a substance of this sort, either carbolic acid, the oil of eucalyptus, a solution of quinia, or thymol. Chlorine (from chloride of lime) used thus has of late been followed by excellent results, and the spray of a solution of corrosive sublimate or of ammonium chloride has been found very useful. The protective treatment should be applied to those exposed to contagion. Such children should be guarded from exposure to colds; their diet should be simple and nourishing, their clothing warm; they should be kept as much as possible in the open air. The breathing of air impregnated with such substances as above mentioned will no doubt act upon the virus before it comes in contact with the mucous membranes so as to be absorbed, and probably the severity of the attack might be mitigated by modifying the germ of the disease.

TREATMENT.—As can be readily imagined, a disease which is so universal, so distressing, and at the same time so obscure in its pathology, as the one under consideration, would have in its literature a mass of recommendations for treatment from zealous advocates, based upon theory or experience, as numerous as the authors themselves. It would be impossible for us to dwell at length upon all of these, but we will confine ourselves especially to the consideration of a few of the most important. It will be convenient to consider first those remedies which have been used with the view of relieving the congestion and irritability of the respiratory mucous membrane and of promoting more free secretion. It will also be observed that many of these remedies may now be regarded as of value for destroying the special germ which is thought to be the essential cause and real virus of pertussis. Allusion has been made above to the importance of inhalations as a prophylactic for those who have been exposed to the contagion, as well as for the purpose of rendering the secretions less contagious; and so too we find that the inhalation of various substances has received favor with many as a method of treatment. Thus, hyoscyamus, belladonna, ammonium bromide have been used. Helenke and Serbaud say that bromide of potassium is best for inhalation. Letzerich recommended the insufflation of quinia twice daily, using the quinia muriate with potassium bicarbonate and gum-arabic. Forchheimer⁷ reports 97 cases of whooping cough treated by the insufflation of the quinia muriate; of the 97 cases, 52 were females, 45 males—the youngest three weeks, the oldest nine years old. Five cases gave no results, while in the others benefit was shown by a shortening or amelioration of the disease. The vapor of benzole has been used with good results. The vapor of carbolic acid has of late been highly recommended, either administered with the atomizer several times daily, or used by saturating flannels in carbolic acid solution and placed around the child's bed at night. It is said that the inhalation of the vapor of a few drops of carbolic acid on some hot coals will ensure a night of freedom from violent coughing. Probably in this way we may account for the belief that proximity to gas-works is beneficial to a child with this disease. As is well known, Niemeyer and others in the north of Germany believed in the value of the inhalation of oxygen, and the experience of every one who has had much to do with this disease favors an out-door life. We may here also mention the value of a small quantity of chloroform or ether, by inhalation, in allaying the severity of the paroxysms of cough. We have also tried the nitrate of amyl, but without marked result.

⁷ New York Jour. Obstet., 1882.

Others have recommended the use of solutions of various substances, applied directly by a brush to the interior of the larynx. Quinia has been used in this way also by Hagenbach; but the most satisfactory results have been obtained by the application of very weak solutions of nitrate of silver, as first recommended by Watson in 1849.

After the secretions have been fully established and the characteristic whoop has appeared, the indications in the treatment are to relieve the respiratory tract of its burden by occasional emesis with alum or ipecacuanha, to give freely antispasmodics and sedatives, as belladonna, chloral, the bromides, hydrobromic acid, or, as recommended by some, digitalis; to give quinia freely, and to use counter-irritants to the neck and chest with liniments composed of oil of amber, croton oil, or turpentine.

The value of emetics has been long recognized in this affection, although we are told by Vogel that the continuous use of emetics in the early stage for several days causes harm. Copeland ordered an emetic every third day in ordinary cases. All writers agree that the milder emetics should be used by preference; that tartar emetic should be avoided, except as an external application where a counter-irritant is desired; and that ipecacuanha is the safest, though alum is also safe and as an astringent useful. Trousseau preferred the sulphate of copper. In the earlier stages of the disease emetics are not, as a rule, indicated; it is only when the secretion has become extremely tenacious, and the paroxysms so frequent and severe as to greatly strain the patient and endanger his lungs, that they are of value. There seems to be a close connection between the amount and tenacity of the secretion and the severity of the paroxysm. The potassium carbonate has been recommended as an active agent in the amelioration of this affection; it is probably valuable in rendering the secretion less tenacious. Alum has been used with success, as has tannin, probably owing to their local action on the mucous membrane. Macartan⁸ says that in the East Indies the disease is treated in the first stages by astringent and tonic gargles.

⁸ Dictionnaire des Sciences Méd., 1813, vol. vi.

Belladonna certainly receives the endorsement of the greatest number of writers. Vogel considers it superior to all other drugs, and regards dilatation of the pupil as the only sure guide in its administration. He says it does not cut short the attack, but mitigates the paroxysm. Trousseau was also an advocate of this form of treatment. When combined with alum⁹ it is considered by Meigs and Pepper to be one of the most valuable drugs recommended. They also advise the use of potassium carbonate. Seiner trusted belladonna more than any other remedy; so also Rilliet and Barthez. William Lee, in an interesting paper in the New York Medical Journal, 1883, advocates the use of atropia hypodermically; he believes that atropia chiefly acts in these cases on the laryngeal branches of the pneumogastric nerves, and that it is probable that it has a decided effect also on the medulla oblongata itself, and renders it less capable of exciting reflex action. Kroon's experiments led him to conclude that the valerianate of atropia was the most useful. Evans¹⁰ gave the 1/120 of a grain of atropia to a child aged three years until the pupils were dilated, then reduced the dose; this stopped the paroxysm in twenty-one days. At the commencement of the treatment the child had twenty-three paroxysms in the day, and twenty-seven at night. Case No. 2 under same circumstances recovered in fourteen days. In case No. 3 the paroxysms were reduced from twenty-six to two or three a day. Arthur Wiglesworth¹¹ used a solution of sulphate of atropia, administered in the morning fasting; the dose he advises for children from one to four years is gr. 1/120, given only once a day except in some cases. The results are as follows: There is a steady diminution in the number of paroxysms; a change in the character of the whoop as if the vocal cords were not so closely approximated. If atropia is withheld, the beneficent effect derived from it subsides.

⁹ Golding Bird, Guy's Hosp. Rep., April, 1845.

¹⁰ Glasgow Med. Jour., 1880.

¹¹ Lancet, April 12, 1879.

West advises dilute hydrocyanic acid, and many writers agree with him, ranking it next to belladonna.

Harley and others are strong advocates for the bromide of ammonium; it is supposed to have a local anæsthetic action on the pharyngeal and laryngeal mucous membrane. Fordyce Grinnell¹² during four months treated 223 cases with this remedy, and highly recommends it. The doses were in accordance with those of Dr. Kormann—¾ to 4 grains, as indicated by age, three or four times a day and at night when the paroxysms were severe. No other treatment was used in these 223 cases, except camphorated oil to the throat and chest in some cases. Potassium bromide has been recommended by Helenke, Beaufort, Erlenmeyer, and others. Henry Field¹³ recommends sodium bromide.

¹² Med. News, 1882.

¹³ Brit. Med. Jour.

Probably next to belladonna in the treatment of this disease we should place chloral hydrate.

Hebner, after an elaborate study of the relative value of potassium bromide, quinia, salicylic acid, chloral, and belladonna, says: "Salicylic acid and chloral tend to relieve the paroxysms—belladonna and quinia to shorten the disease." Kennedy¹⁴ writes: "I cannot doubt its specific effects on the cough. Chloral seems to me to yield the best and most constant results. The advantage of chloral hydrate seems to exist in producing sleep; it should be given in from 2- to 5-gr. doses, at night." If there is much irritability or fretfulness, or any premonition of eclampsia, it should be associated with potassium bromide.

¹⁴ Dublin Jour. M. S., 1881.

Croton chloral has received much praise from those who have used it; we have had no experience with it.

We have already alluded to the value of quinia, which has been used largely in this disease, both internally and as a local application. Originally recommended in the latter manner on account of its power of controlling the development of low organisms, it has not proved so satisfactory or valuable as when given internally. Binz in 1870 was perhaps the first to recommend quinia given frequently and in solution, and Dawson in 1873¹⁵ reports excellent results from the sulphate or muriate of quinia given in full and frequent doses, and in such solutions as will not prevent its acting on the mucous membrane in its passage through the pharynx. Breidenbach¹⁶ gives the quinia muriate in larger doses—one and a half to fifteen and a half grains per diem. The effects were surprising as soon as the proper dose for each person had been determined; this, he says, is the keynote of success. To prevent complications he continued it for a long time in small doses.

¹⁵ Am. Jour. Obstetrics.

¹⁶ Practitioner, Feb., 1871.

Our own experience favors the view that quinia, when given in solution or suspended in mixture, is valuable in many cases of this disease; it can be ordered in powder, and given in a spoonful of simple syrup or of the preparation known as the syrup of yerba santa, which makes an excellent vehicle. Liquorice also disguises the taste of quinia admirably for children.

Albrecht¹⁷ has found from an experience of ten cases of whooping cough in children between the ages of one and a half and nine years, all of a marked scrofulous type, much benefit from the muriate of pilocarpine, given in small doses after every fit of coughing. To prevent collapse, he advises that it should be given in a mixture containing a little brandy. After twenty-four hours of its administration an obvious change for the better takes place in the appearance of the mucous membrane of the throat, velum palati, and uvula, which becomes paler, less swollen, and more moist; laryngoscopic examination shows a similar improvement. During the catarrhal period cold compresses to the neck and sweetened milk containing potassium chlorate are used instead of the pilocarpine, which is to be resumed as soon as a whoop recurs.

¹⁷ London Med. Rec., March 15, 1882, p. 110.

Dr. Tordeus, of the Hospice des Enfants Assistés, Brussels, states that he has found the sodium benzoate useful in whooping cough, diminishing the frequency and violence of the paroxysms, and by its action on the pulmonary mucous membrane preventing those pulmonary complications which so frequently supervene and constitute the danger of the disease.

Sulphur has been largely used by the Germans in two- or three-grain doses, and is said to be greatly esteemed by them. Cantharides has been recommended, and it is stated that when strangury is produced the whoop will cease; we should consider this rather severe treatment. The fluid extract of castanea is used by many with undoubtedly good results, though this also has been somewhat of a disappointment in the way of treatment, as at one time it was looked upon almost as a specific. Many claim that an infusion of the fresh leaves gives a better result. Dewar¹⁸ regards ergot with great favor in the treatment of pertussis. Certainly in those cases where, from violent straining, hemorrhages have taken place we have found it to be highly valuable. We have had no experience with it in the treatment of ordinary cases, though Dewar claims that it shortens the attack. The ammonium picrate, and recently resorcine, have been used with success.

¹⁸ The Practitioner, London, May, 1882.

Counter-irritation to the neck and chest has always been found useful in the treatment of this disease. Autenreith¹⁹ recommends tartar emetic to the epigastrium till vesicles appear and even ulcerate. Milder forms of counter-irritation over the chest seem equally efficacious if continued for some time. The oil of amber, when used in liniment with camphor or turpentine, is by some considered almost a specific. Great care should also be observed in the dress of children with whooping cough. Warmth about the chest is always indicated, while there should be nothing close or tight about the throat allowed.

¹⁹ Dict. des Sciences Med., 1813.

In the third stage, when there is the nervous element remaining, tonics, such as cod-liver oil, iron, the phosphates and hypophosphites, are required.

The diet should be nutritious, easy of digestion, and abundant, and the bowels should be kept regular by fruits or laxatives. Over-feeding should of course always be avoided, and the attempt at weaning a babe with this disease would certainly meet with unfavorable results.

Bicarbonate of soda or lime-water should be given freely with the milk taken by children with this disease. Milk certainly should form the basis of the diet of children with pertussis, and reliable meat-extracts are to be recommended in this disease even for older children, who from the severity of the attack would vomit more solid food. If the vomiting be so severe as to affect nutrition, the child should be sustained by peptonized milk, soup, or gruel, given by the bowel.

The importance of a proper regulation of the temperature of the air which the patient breathes is especially recognized in France. If the attack occurs in mid-winter and the seashore be inaccessible or inexpedient, the child should be restricted to a well-ventilated nursery or suite of rooms, the temperature of which should be kept uniform.

Salt air is recognized to be of great value in advanced cases of this disease; this has been attributed partly to the effects of stimulation of the mucous membrane in rendering less viscid and more copious the bronchial secretions, and also to the balmy softness and great purity of the atmosphere at the sea-shore. But probably there is another element in the local action of the chloride of sodium, either in establishing a resistance on the part of the patient or in modifying the germ of the disease.

The most serious complication of whooping cough is pneumonia. It occasionally happens that an attack of croupous pneumonia may develop during the course of whooping cough, but in the vast majority of cases the disease is of the catarrhal type. When, indeed, it is remembered that a bronchial catarrh, which is the invariable precursor or accompaniment of catarrhal pneumonia, is a constant factor in whooping cough, and, further, that all conditions of debility, and especially of enfeebled or embarrassed respiration, dispose to this form of pneumonia, it is not surprising that this complication should be of such frequent occurrence. It is not impossible that in aiming at securing sufficient fresh air and out-door exercise to maintain the general health, an injudicious degree of exposure may be permitted which will aggravate the existing bronchitis and induce an extension of inflammation to the alveoli. But usually the catarrhal pneumonia develops in a subacute and more or less insidious manner, and without being traceable to any such exposure. It may happen occasionally that in the violent inspiratory efforts at the close of the paroxysms irritating secretions may be sucked from the bronchioles into the alveoli, and there excite inflammation. Or, again, it doubtless happens frequently that, with the existence of swelling of the bronchial mucous membrane and of viscid secretions in the bronchial tubes, collapse of portions of lung tissue is developed by the forcible expulsion of air during the paroxysms of cough, which cannot be replaced owing to the relative weakness of inspiration and to the ball-valve action of the plugs of mucus in the obstructed bronchioles. The intimate relation between pulmonary collapse and catarrhal pneumonia is familiarly known. It is not to be considered that the mere occurrence of collapse will induce pneumonia in the areas affected, but certainly it will aid in rendering effective the other irritating causes. As a consequence, it usually happens that when catarrhal pneumonia occurs in whooping cough it is associated with more or less collapse. When, then, especially in children of debilitated or rachitic constitution, or in those who are subjected to unfavorable hygienic influences, such as overcrowding, bad air, and the like, there is a rather gradual development of dyspnoea, with increasing debility, emaciation, and evidences of impaired oxygenation of the blood, it is to be feared that this serious complication has developed. The physical signs are often difficult of interpretation, but if careful examination of the chest be conducted, together with thermometric observations, the approach of this danger or its actual presence may be detected. The result is fatal in a large proportion of cases, so that suitable treatment—for the details of which reference is made to the appropriate section—must be instituted without delay.

Our investigations of this disease have led us to the conclusion that we have to deal with an affection caused by a specific germ, which is usually, after a period of incubation, made manifest by a catarrh of a portion of the air-passages; that this catarrh, existing for an indefinite period, is capable of being influenced by medication, applied either by means of inhalation or by acting on the mucous membrane after absorption by the stomach. In this way we have known the administration of quinia and of alum diminish the number of paroxysms, to all appearance checking the excessive secretion to a marvellous extent. The other element of the disease, the neurosis, which soon follows the initial catarrh, and seems to last for an indefinite time after the mucous membrane has regained its normal appearance, is also capable of being controlled by the use of drugs, especially belladonna, chloral, the bromides, and hydrocyanic acid, not to speak of the other antispasmodics and sedatives, and by the analgesic effect of carbonic acid gas, or by the spray of bromide of ammonium, carbolic acid, and other substances upon the larynx.

Vogel tells us in his classical work on children, "If now, as a résumé, I would give an explanation of my views, it would go to show that there never has been, and most probably never will be, a remedy by which whooping cough may be abridged, any more than we are able to cut short the acute exanthemata or typhus fever or pneumonia." And yet the experience of many whom we have quoted in this article tends to support the view that by a form of treatment calculated to act on the two elements of the disease which we have just noted, the affection can be greatly modified in its intensity, and probably the attack be somewhat shortened. Certain it is that the recent studies of this disease give us hope that the day is not far distant when the cause, whatever it is, will be definitely known, and if it is found to reside in the secretions from the larynx, that treatment by inhalation or atomization will modify or destroy it, and prevent its dissemination.

INFLUENZA.

BY JAMES C. WILSON, M.D.

DEFINITION.—A continued fever, occurring in widely-extended epidemics, and due to a specific cause; it is characterized by early catarrh of the mucous membrane of the respiratory tract, and in many cases also of the digestive tract; by quickly oncoming debility out of proportion to the intensity of the fever and the catarrhal processes; and by nervous symptoms. There is a strong tendency to inflammatory complications, especially of the lungs. Uncomplicated cases are rarely fatal except in feeble and aged persons. An attack does not confer immunity from the disease in future epidemics.

SYNONYMS.—Febris catarrhalis; Defluxio catarrhalis epidemicus; Catarrhus a contagio; Rheuma epidemicum; Cephalalgia contagiosa; Epidemic catarrhal fever; Tac; Horion; Quinte; Coqueluche; Ladendo, also written La Dando; Baraquette; Générale; Coquette; Cocotte; Allure; Follette; Petite poste; Petit courier; Grenade; La Grippe; Ziep; Schaffhusten and Schaffkrankheit; Huhner-Weh; Blitz-Katarrh; Mödefieber; Mal del Castrone. There are also several names indicating its supposed origin; thus it has been called in Russia, Chinese catarrh; in Germany and Italy, the Russian disease; in France, Italian fever, Spanish catarrh, and so forth.

It is a remarkable fact that in two instances at least the popular name for the disease under consideration has found its way widely into medicine and medical literature, almost to the exclusion of the studied terms by which science has sought to designate it; these are influenza and la grippe.

Such obsolete and now meaningless terms as Peripneumonia notha (Sydenham, Boerhaave), Peripneumonia catarrhalis (Huxham), Pleuritis humida (Stoll), have been omitted from this list of synonyms as being of interest rather to the student of medical history than to the student of medicine.

Febris catarrhalis, Defluxio catarrhalis epidemicus, Rheuma epidemicus are terms which no longer retain the place given them in the literature of influenza by the older medical authorities.

Catarrhis a contagio (Cullen) and Cephalalgia contagiosa are derived from a view of the nature of the disease, which has been the cause of no little controversy.

Epidemic catarrhal fever is, with its Latin equivalent, the most satisfactory of the so-called scientific names by which the disease is at present known.

In the popular names for the affection there is to be noted an indication of the national character of some of the peoples who have suffered from its frequent visitations.

Among the English it is known as cold or epidemic cold, or, in deference to medical authority, as catarrh or epidemic catarrh; and at present, both among the folk and the doctors, as influenza. Englishmen are neither quick to see in the disease a resemblance to some common circumstance or thing, nor are they disposed to make a joke about it.

The Germans find obvious resemblances. In the labored respiration and the character of the cough they find a suggestion of a common epizoötic affecting the sheep, hence Schaffhusten and Shaffkrankheit; or, because the cough is like the crowing of a cock and the disturbance of respiration and rapid prostration suggest some resemblance to a common disease of the domestic fowl, it has been called Huhner-Weh (chicken disease, whooping cough), and Ziep, which is about equivalent to pip. They call it also, from its rapid invasion, Blitz-Katarrh, and from its diffusion, Mödefieber.

The French are disposed to make a jest of everything, and the more serious the subject the better the joke. Hence they have found a new name for almost every great epidemic, and each more trivial than the last. Thus, tac (rot); horion (in jest, a blow); quinte, because the spells occur at intervals of five hours (sic); coqueluche (a hood or cowl), from the cap worn by those suffering from the malady; and so on through the long list given above.

La grippe is said to be derived from the Polish Chrypka (Raucedo); it may, however, be derived from agripper (to seize).

Influenza is of Italian derivation. It is said that the disease received this name because it was attributed to the influence of the stars, or from a secondary signification of the word indicating something fluid, transient, or fashionable.

HISTORICAL SKETCH.¹—Epidemics of influenza have been clearly recorded only since the beginning of the sixteenth century. There are numerous accounts of earlier epidemic diseases resembling it, but they are not sufficiently particular to warrant us in inferring its undoubted existence. It is supposed to be referred to in the writings of Hippocrates, who, however, gives no exact description.² An outbreak in the Athenian army in Sicily (415 B.C.), recorded by Diodorus Siculus, has been supposed to have been influenza. Despite these statements, and those of others to the effect that it is a disease known from a remote antiquity, it may be said that no accounts can be confidently established, as referring to the disease now known as influenza, in the writings of classical antiquity.³

¹ See also The Continued Fevers, by the author of this paper, New York, 1881.

² Parkes, Reynolds's System of Medicine, vol. i., 1868.

³ Zuelzer, Ziemssen's Cyclopædia of Medicine, vol. ii., 1875.

As early as the ninth century several epidemics of catarrhal fever, Italian fever, and the like, which were probably influenza, were made matter of history. In the year A.D. 827 a cough which spread like the plague was recorded. In 876 there appeared in Italy a similar epidemic, which spread with great rapidity over all Europe. It is related that dogs and birds suffered with symptoms not unlike those characterizing the affection in man. In 976, Germany and all France suffered from a fever of which the chief symptom was cough. No further epidemic is noted until two centuries later, when, in 1173, a widespread malady, of which the symptoms were chiefly catarrhal, raged throughout Europe; while less important epidemics of a like character are recorded as having occurred during the following century (1239-99).

In the medical writings of the fourteenth century there are to be found records of six epidemics, and in the fifteenth seven great visitations of influenza are described (Parkes).

Aitken⁴ speaks of a very fatal prevalence of influenza throughout France in 1311, and of an epidemic in 1403 in which the mortality was so great that the courts of law in Paris were closed in consequence of the deaths.

⁴ Aitken's Practice of Medicine, vol. i., 1872.

Influenza is mentioned in the Annals of the Four Masters as having prevailed in Ireland in the fourteenth century, and a disease characterized by similar symptoms is alluded to in early Gaelic manuscripts under the name of Creatan (creat, the chest). The disease is described also in an Irish manuscript of the fifteenth century under the terms Fuacht and Slaodan.⁵

⁵ Theophilus Thompson, Annals of Influenza, 1852.

The earliest epidemic that prevailed in the British Isles of which any accurate description remains is that of the year 1510. The disease came from Malta, and invaded first Sicily, then Italy and Spain and Portugal, whence it crossed the Alps into Hungary and Germany as far as the Baltic Sea, extending westward into France and Britain. Its track widened over the whole of Europe from the south-east to the extreme north-west, and it is said that not a single family and scarce a person escaped it. It was attended by a "grievous pain in the head, heaviness, difficulty of breathing, hoarseness, loss of strength and appetite, restlessness, retchings from a terrible tearing cough. Presently succeeded a chilliness, and so violent a cough that many were in danger of suffocation. The first day it was without spitting, but about the seventh or eighth day much viscid phlegm was spit up. Others (though fewer) spat only water and froth. When they began to spit, cough and shortness of breath were easier. None died except some children. In some it went off with a looseness, in others by sweating. Bleeding and purging did hurt."⁶ Blisters were commonly employed—two each upon the arms and legs, and one to the back of the head. The description is sufficiently clear to place the nature of this epidemic beyond all doubt.

⁶ Thomas Short, A General Chronological History of the Air, Weather, Meteors, etc., London, 1749; quoted in the Annals of Influenza.

The epidemic of 1557, starting westward from Asia, spread over Europe, and then crossed the Atlantic to America. The malady broke out in England, after a season of unusual rain and great scarcity of corn, in the month of September. "Presently after were many catarrhs, quickly followed by a more severe cough, pain of the side, difficulty of breathing, and a fever. The pain was neither violent nor pricking, but mild. The third day they expectorated freely. The sixth, seventh, or at the farthest the eighth day, all who had that pain of the side died, but such as were blooded on the first or second day recovered on the fourth or fifth; but bleeding on the last two days did no service." "Some, but very few, had continual fevers along with it; many had double tertians; others simply slight intermittent. All were worse by night than by day; such as recovered were long valetudinary, had a weak stomach, and hypped." Gravid women either aborted or died. This epidemic spread with frightful rapidity. Thousands were attacked at the same time. The entire population of Nismes, with scarcely an exception, fell ill of it upon the same day. It was extremely fatal. In Mantua Carpentaria, a small town near Madrid, it broke out in August, and so fatal were the bloodletting and purging which constituted the treatment at first, that, of the two thousand persons who were bled, all died. The disease raged in some parts till the middle of the following year (1558), and carried off, in Delft alone, five thousand of the poor. In all cases mild treatment was called for, with warm broths and speedy immersals, "to recall the appetite and keep the vessels of the throat open."

In 1580 a great epidemic of influenza spread from the south-east toward the north-west over Asia, Africa, and Europe. From Constantinople and Venice it overran Hungary and Germany, and reached the farthest regions of Norway, Sweden, and Russia. It spread into England, and has been described by Dr. Short. In Italy it prevailed during August and September, in England from the middle of August to the end of September, and in Spain during the whole summer. In most places its duration was about six weeks. As a rule, the termination was favorable, although the disease ran a somewhat protracted course. In the account of Dr. Short it is stated that "few died except those that were let blood of or had unsound viscera." In some places, on the contrary, the course of the disease was very severe. In Rome two thousand died of it, according to the author just cited, but Zuelzer informs us that the victims of this epidemic in the Eternal City were not less than nine thousand, and adds that Madrid must have been almost depopulated by it. This high mortality has been attributed to the bloodletting practised in the treatment of the disease. The symptoms were similar to those of the previous epidemics, with a greater shortness of breath, which continued in many cases for some time after the disappearance of the catarrhal trouble. There was great sweating at the end of the attack. The plague, measles, and small-pox prevailed also, and with considerable violence, during the year 1580.

Influenza, unfelt for several years, reappeared in Germany in 1591; an epidemic extending from Holland through France and into Italy occurred in 1593. In 1610 catarrh is said to have prevailed throughout Europe. In 1626-27 epidemic catarrhal fever made its appearance in Italy and France; in 1642-43 in Holland; in 1647 in Spain and in the colonies of the Western World; and again, in 1655 in North America. According to Webster,⁷ this epidemic of 1647 was the first catarrh mentioned in American annals.

⁷ Noah Webster, A Brief History of Epidemic and Pestilential Diseases, London, 1800.

In 1658 and 1675 it again visited Austria, Germany, England, etc. The first of these two epidemics is described by Willis,⁸ and the second by Sydenham,⁹ as they occurred in England, and the accounts are to be found in the Annals of Influenza. It is about this period that the disease began to be known as influenza, and it is not without interest to observe that the influence of the stars suggested itself, in connection with its sudden appearance and wide prevalence, to the minds of the physicians of this date. Willis writes that "about the end of April (1658), suddenly a distemper arose, as if sent by some blast of the stars, which laid hold on very many together; that in some towns in the space of a week above a thousand people fell sick together."

⁸ Dr. Willis, The Description of a Catarrhal Fever Epidemical in the Middle of the Spring in the Year 1658: Practice of Physick, 1684.

⁹ The Epidemic Coughs of the Year 1675, with the Pleurisy and Peripneumony that supervened: from the Works of Thomas Sydenham, M.D.

Epidemics are recorded as having occurred in Great Britain and Europe in 1688, 1693, and in 1709. The disease raged in 1712 widely over Europe from Denmark to Italy.

In 1729-30 a widespread epidemic swept over Europe. In five months it extended over Russia, Poland, Germany, Sweden, and Denmark. In Vienna sixty thousand persons fell ill of it. In the autumn it spread to England, and reached France and Switzerland; from there it extended to Italy, and by February it had reached Rome and Naples. Spain did not escape its ravages, and it is said to have found its way to Mexico. The symptoms did not differ in any important respect from those already described as characterizing previous epidemics. Pains in the limbs and fever marked the onset of the attack; catarrh, oppression, hoarseness, cough followed. In some cases delirium, drowsiness, and faintings occurred. A petechial eruption was observed, in some instances, between the fourth and seventh days. This renders it probable that typhus or cerebro-spinal fever prevailed at the same time. Turbid urine, copious sweats, bilious stools, and nose-bleeding were often noted. In Switzerland only children and old persons died. The disease was not very fatal.

Two years later (1732-33) an epidemic, starting from Saxony and Poland, overran Germany, Switzerland, and Holland, and invaded Great Britain in the month of December. Toward the end of January it spread in a south-easterly direction to France, Italy, Spain, and westward to North America, thence southward to the islands of the West Indies, and on to South America. The course of the disease in this epidemic was favorable. The attack terminated in from three to fourteen days, with sweating, bleeding from the nose, or an abundant discharge from the nasal passages. The aged and those suffering from chronic pulmonary diseases mostly perished. In Scotland three forms of the affection were described—namely, the cephalic, the thoracic, and the abdominal. The epidemic slowly spread over Eastern Europe and in a south-easterly direction, and may be said to have lasted till 1737.

Concerning this epidemic John Huxham of Plymouth wrote as follows:¹⁰ "About this time a disease invaded these parts which was the most completely epidemic of any I remember to have met with; not a house was free from it; the beggar's hut and the nobleman's palace were alike subject to its attacks, scarce a person escaping either in town or country; old and young, strong and infirm, shared the same fate." The malady had raged in Cornwall and the western parts of Devonshire from the beginning of February; it reached Plymouth on the 10th, which was on a Saturday, and that day numbers were suddenly seized. The next day multitudes were taken ill, and by the 18th or 20th of March scarcely any one had escaped it. "The disorder began at first with a slight shivering; this was presently followed by a transient erratic heat and headache and a violent and troublesome sneezing; then the back and lungs were seized with flying pains, which sometimes attacked the heart likewise, and though they did not long remain there, yet were very troublesome, being greatly irritated by the violent cough which accompanied the disorder, in the fits of which a great quantity of a thin, sharp mucus was thrown out from the nose and mouth. These complaints were like those arising from what is called catching cold, but presently a slight fever came on, which afterward grew more violent; the pulse was now very quick, but not in the least hard and tense like that in a pleurisy; nor was the urine remarkably red, but very thick, and inclining to a whitish color; the tongue, instead of being dry, was thickly covered with a whitish mucus or slime; there was an universal complaint of want of rest and a great giddiness. Several likewise were seized with a most racking pain in the head, often accompanied by a slight delirium. Many were troubled with a tinnitus aurium, or singing in the ears; and numbers suffered from violent earaches or pains in the meatus auditorius, which in some turned to an abscess. Exulcerations and swellings of the fauces were likwise very common. The sick were in general very much given to sweat, which, when it broke out of its own accord, was very plentiful and continued without striking in again, and did often in the space of two or three days wholly carry off the fever. You have here a description of this epidemic disease such as it prevailed hereabouts, attacking every one more or less; but still, considering the great multitude that were seized by it, it was fatal to but few, and that chiefly infants and consumptive old people. It generally went off about the fourth day, leaving behind a troublesome cough, which was very often of long duration, and such a dejection of strength as one would hardly have suspected from the shortness of the time.

"On the whole, this disorder was rarely mortal, unless by some very great error arising in the treatment of it; however, this very circumstance proved fatal to some, who, making too slight of it, either on account of its being so common or not thinking it very dangerous, often found asthmas, hectics, or even consumptions themselves, the forfeitures of their inconsiderate rashness."

¹⁰ Observations on the Air and Epidemical Diseases, translated from the Latin, London, 1758.

Arbuthnot also described this visitation of the disease.¹¹ He regarded the uniformity of the symptoms in every place as most remarkable, and tells us that during the whole season in which it prevailed there was "a great run of hysterical, hypochondriacal, and nervous distempers; in short, all the symptoms of relaxation."

¹¹ An Essay concerning the Effects of Air on Human Bodies, London, 1751.

During the years 1737-38 influenza again swept over England, North America, the islands of the West Indies, and France; in 1742-43 it prevailed in Western Europe and the British Isles; in 1757-58 in North America, the West Indies, France, and Scotland. In 1761 it overran the North American colonies and the West Indies.

The epidemic of 1762 extended very generally over Europe and Great Britain. In Germany nine-tenths of the population were attacked by the disease.

Widely extended epidemics prevailed in Europe and America in 1767 and 1775; in 1772 it raged in North America; in 1778-80, in France, Germany and Russia. Noah Webster found influenza prevalent in North America in 1781; the next year one of the most remarkable epidemics of this disease (described as the epidemic of 1782) appeared in Europe. It came from the East, from Asia into Russia. From St. Petersburg it spread during the winter and spring over Sweden, Germany, Holland, and France. In the autumn it was in Italy, Spain, and Portugal. The crews of Dutch and English ships were taken ill with the disease upon the high seas.

In Vienna three-fourths of the population fell ill of it with such suddenness that it got here for the first time its name of "Blitz Katarrh" (lightning catarrh). It was characterized by great pain in the back, breast, and throat, and by extraordinary enfeeblement. Relapses occurred, and inflammation of the lungs and bowels was common. Children remained relatively exempt from its seizure. This epidemic broke out in England about the end of April and raged until the end of June. "The duration of the malady in some was not above a day or two, but it usually lasted near a week or longer. In a few the symptoms seemed to abate in two or three days, but some returned and raged with more violence than at first."¹² The disease was not regarded as in itself fatal, and few could be said to have died of it "but those who were old, asthmatic, or who had been debilitated by some previous indisposition."

¹² An Account of the Epidemic Disease called the Influenza of the Year 1782. Collected from the Observations of several Physicians in London and in the Country, by a Committee of the Fellows of the Royal College of Physicians in London. Read at the College, June 25, 1783.

Numerous recurring outbreaks took place in Europe and America during the years 1788-90. One of these, as it occurred in America, is well described by Dr. John Warren¹³ of Boston in a letter to Lettsom. This letter is dated May 30, 1790, and among other matters of great interest respecting the disease it is stated that "Our beloved President Washington is but now on the recovery from a very severe and dangerous attack of it in that city" (New York).

¹³ Memoirs of the Life and Writings of J. Coakley Lettsom, Thomas Joseph Pettigrew, 1817.

Webster mentions an epidemic in America in 1790, one in Europe in 1795, and another in Europe in 1797, but there seems to have been no general epidemic of sufficient importance to attract the attention of other writers upon the subject until 1798, when the malady again broke out in Russia and spread over the greater part of Europe, continuing to prevail in various regions till 1803, when it again appeared in England, and is described by several writers of that country.

From 1805 to 1827 influenza prevailed (according to Zuelzer, who tells us that few years during this interval were free from it) in frequently-recurring epidemics in Europe and America. Thompson mentions no visitation in England between 1803 and 1831.

In the year 1830 began a series of epidemics remarkable for their wide diffusion and the rapid succession with which they followed one upon another. The disease began in China; in September it reached the Indian Archipelago; it swept into Russia, and invaded Moscow in November; in January, 1831, it was raging in St. Petersburg; March found it in Warsaw; April in Eastern Prussia and Silesia; in May it prevailed in Denmark, Finland, and a great part of Germany, and in the same month it fell upon Paris; in June it affected England and Sweden; it was still creeping about Middle Europe and lingering in Great Britain at the end of July; in the early winter it swept southward into Italy, and westward across the Atlantic to North America, and was still harassing the inhabitants of certain regions of the United States in January and February, 1832. Meanwhile it continued in the East, spreading to Java, Farther India, and the Indian Archipelago. It continued in Hindostan after it had died out in Europe. But in January, 1833, it again visited Russia, and rolled thence southward and eastward over the most of Europe. It is recorded that by February it had reached Galicia and Eastern Prussia; in March it was in Prussia, Bohemia, and Warsaw, and had extended to Syria and Egypt; in April to many parts of Germany and Austria and to France and Great Britain. Midsummer found the disease yet prevailing in some districts of Germany and Northern Italy, and in the early autumn it was in Switzerland and Eastern France; in November it visited Naples.

Epidemics so frequent, so widespread, and so unsparing of individuals wherever the disease appeared could not fail to excite a deep and general interest. From this period the literature of the subject has been voluminous.

A brief period of repose ensued. For three years no epidemic occurred which was of sufficient importance to attract the attention of medical historians.

In December, 1837, influenza reappeared, and first, as so often before, in Russia; Sweden and Denmark were almost simultaneously affected; in January, 1837, it broke out in London, and rapidly swept over all England and into France and Germany. In January it appeared in Berlin, and shortly afterward in Dresden, Munich, and Vienna. The disease spread by February into Switzerland, and into Spain as far as Madrid by the end of March. In London almost the whole population was attacked, and the mortality was enormous. It is stated that the deaths were quadrupled during the prevalence of the disease. Large populations suffered most. This epidemic spread into the southern hemisphere, and prevailed at the same time, and consequently at exactly the opposite season that it prevailed north of the equator, in Sydney and at the Cape of Good Hope.

From 1837 to 1850-51 numerous epidemics of influenza occurred. Few years were exempt from them. The epidemic of 1847-48 has been described by many writers, and more particularly, as it occurred in London, by Peacock¹⁴ with great exactitude. It is estimated that one-fourth of the entire population of that city were more or less affected by the disease. The epidemic prevailed in London for six months, and, although the deaths registered for the entire period as from influenza amounted to only 1739, it is stated in the report of the registrar-general that during the six weeks the epidemic was at its height not less than five thousand persons died, in the metropolitan districts, in excess of the average mortality of the period, the excess showing itself in nearly every class of disease, the local maladies which had been the predominant affections being doubtless in many cases assigned as the cause of death. This epidemic affected between one-fourth and one-half of the population of Paris, and in Geneva the proportion of those attacked was not less than one-third of the entire population.

¹⁴ On the Influenza, or Epidemic Catarrhal Fever of 1847-48, Thomas Berill Peacock. M.D., 1848.

More or less widespread epidemics of influenza are recorded as having occurred in 1857-58 and 1860; in 1864 in Switzerland; in 1867 in Paris in the spring; and at various times in the United States and Canada.

A mild epidemic occurred in 1874 in Berlin.

Influenza prevailed over a wide area in the United States during the early months of 1879. The characteristics of this visitation have been well described by Da Costa.¹⁵

¹⁵ "The Prevailing Epidemic of Influenza—Its Characteristic Phenomena—Pulmonary, Gastro-intestinal, Cerebral, and Nervous—Its Wide Distribution, Mortality, and Treatment," Medical and Surgical Reporter, Philadelphia, March 8, 1879.

The disease, since the great epidemic of 1847-48, has affected a smaller proportion of the inhabitants of the localities visited, and has run a less dangerous course, than in the earlier epidemics. It has for this reason occupied a less conspicuous place in the medical literature of recent years. It is nevertheless true that even in the mildest epidemics, when a relatively small number of persons are seized and the symptoms are in most cases almost insignificant, cases do here and there occur which are of a serious or even fatal character, and that the death-rate from other diseases is for the time considerably increased.

Catarrhal affections have often prevailed among the domestic animals when influenza has been epidemic. Horses, dogs, and cats are subject to these disorders; neat cattle, goats, and sheep have been less commonly affected; chickens and pheasants have suffered, and it is stated by some of the older writers that birds, and particularly the sparrow, have deserted localities in which influenza was prevailing, and that migratory birds have taken flight earlier than usual.

These epizoötics have sometimes preceded the appearance of influenza among men by a period of some weeks or days; in other instances they have appeared at the same time; and in a widespread outbreak among horses in the United States in 1872, in which the symptoms and morbid anatomy, accurately observed, were undoubtedly those of influenza, the disease did not affect man except to a very limited extent. A want of fulness of description, and the inaccuracy of diagnosis too common in the consideration of the general diseases of the lower animals, leave the precise nature of most of the epizoötics described by the earlier writers doubtful.

An extensive influenza of moderate intensity prevailed as an epizoötic, chiefly affecting horses, during the latter part of the summer and the autumn of 1880 in Canada and the United States east of the Mississippi River. Dogs were also affected, but less generally, and human beings to a still slighter extent. In several localities where this invasion was observed by the writer the horses were first affected, the dogs next, and after the lapse of some weeks, as the animals were recovering, the disease became epidemic; but those persons who took care of horses and were much in contact with them neither suffered earlier nor more severely than others not so exposed.

ETIOLOGY.—1. Predisposing Influences.—There are no well-established facts pointing to the existence of individual peculiarities that can be regarded as predisposing influences. When the disease appears a large proportion of the population is attacked without distinction of age, sex, social condition, or occupation. Previous illness, whether acute or chronic, local or constitutional, affords no protection. Aged and infirm persons and those of nervous temperament are peculiarly liable to attack, but the robust possess no immunity. All races and dwellers in every climate are the victims of influenza. In a community invaded by the disease females are apt to be the first attacked, adult males next, and children last. It has been observed that in some epidemics children are but little liable to contract the disease.

An attack confers no exemption from the disease in another epidemic, and independently of relapses, which are not infrequent, persons have been known to experience a second attack during the prevalence of the same epidemic.

Persons dwelling in overcrowded and ill-ventilated habitations and in low, damp and unhealthy situations have, in certain epidemics, especially suffered, and the increase of deaths by influenza is proportionately much greater in districts in which there is ordinarily a high mortality than in healthier places.

Influenza appears at all seasons of the year and affects the inhabitants of every latitude. It has no connection with known atmospheric conditions. Many of the earlier writers sought to establish a relation between low temperatures and sudden variations of temperature and influenza, and by reason of the confusion among the people between these diseases and common "colds" there has always existed an opinion that such a relation obtains. There is, however, no evidence to sustain this view; neither low temperature nor abrupt changes give rise to the affection. It has prevailed in hot and dry seasons, in the West Indies, on the coast of Java, in India, in Egypt, at the Cape of Good Hope, on the Riviera in summer.

The condition of the air as regards moisture, or dryness, does not influence the spread of the disease. It has occurred at sea, on low sea-coasts, and in the dryest climates, as, for example, in Upper Egypt.

Its spread is not much influenced by local winds. It does not travel with the same velocity, and even sometimes advances against them. In several well-authenticated instances a dense and foul fog has preceded and attended the local outbreak of epidemics. The much greater number of epidemics that have occurred altogether without such manifestations make it in a high degree probable that this has been a coincidence. Ozone in large quantities artificially produced may give rise to the symptoms of ordinary catarrh, but it is not a cause of influenza. The disease is not in any way connected with the condition of the soil, elevation, volcanic eruption, or any other local cause. The history of every epidemic may be adduced in proof of this statement.

Before taking up the consideration of the exciting causes of influenza, it is important to review the known facts concerning the march of epidemics and the spread of the disease in affected localities. It has prevailed with greater or less frequency in almost every region of the globe. Epidemics recur at irregular periods. It was at one time supposed that the course of the disease was cyclical, with a return at intervals of about one hundred years. This view was long ago proved to be unfounded. About every twenty-five or thirty-five years great epidemics have swept over vast areas of the globe, and influenza may be said to be, at such times, pandemic. Less-widely extended epidemics have taken place with greater or less frequency in the intervals between the great outbreaks. But it is not possible to establish anything like a regular periodicity in the returns of the disease.

It has been supposed in some instances to prevail within restricted localities, as, for example, in a single city. Such local epidemics are without doubt due to local causes, and are of the nature of simple ordinary catarrhal fever, rather than true influenza.

The epidemics have extended over great areas, usually in a direction from the east or north-east toward the west and south. At other times they take the opposite course, and in some years they have appeared to radiate in various directions from several centres. It is in consequence of these facts that two views have arisen concerning the origin of the affection. The first of these is, that each epidemic starts out from some single unknown source, and spreads thence from point to point, invading more distant localities successfully as it advances, until at length it dies out in regions remote from the starting-point. This opinion is in accord with the popular belief. Thus, the Italians have called it the German disease; the Germans, the Russian pest; the Russians, the Chinese catarrh. The geographical relation of these nations indicates the usual track of the great epidemics, as shown in the foregoing historical sketch. The other opinion is, that it arises not from some single particular place, but that it may start anywhere, and that widespread epidemics are due to the successive outbreaks of the disease at many distinct points of origin.

The evidence that the great epidemics of influenza are due to some general and pandemic influence is conclusive. The point of origin of the great epidemics has not yet been indicated with precision, and must remain beyond conjecture until further facts bearing upon the question of their source are brought to light. When it has prevailed over a large portion of the earth's surface its progress from place to place has usually been rapid. In this respect, however, the epidemics show a great diversity. It sometimes travels exceedingly slowly. It is said to have overrun Europe in six weeks, and it has again taken six months to do so. It sometimes attacks places widely remote from each other within short intervals of time, and it has appeared at the same time in different quarters of the globe. It does not follow the great lines of travel and commercial intercourse.

When influenza enters a city it continues to prevail, as a rule, from four weeks to two months, but exceptionally it remains a longer time; for example, the epidemic of 1831 was prevalent in Paris for the greater part of the year. It in all instances finally disappears, and sporadic cases do not occur in the intervals between the epidemics.

In rare instances the epidemics are heralded by scattered cases. But as a rule this disease attacks simultaneously great numbers of the inhabitants of affected districts, so that, when the epidemic is severe, the sick are in a short time to be counted by thousands and business is paralyzed as by a blow. Epidemics rapidly reach their height, and subside almost as suddenly as they began. In a large city the disease frequently, perhaps always, makes its appearance nearly at the same time in several different localities, affecting certain streets and quarters solely or more generally than others for a time, and spreading thus from several centres through the entire community. Large towns and cities are generally affected earlier than the villages around them, and the latter, though closely adjacent, sometimes escape for weeks. The crews of ships upon the high seas, not sailing from an infected port, are said to have suffered from the seizure, and epidemics have many times crossed the Atlantic from the Old World to the New, and more than once in the opposite direction.

2. The Exciting Cause.—Large as has been the place in medical literature occupied by the histories of epidemics of influenza, the nature of the "epidemic influence" which gives rise to the disease is still unknown.

The question of the contagiousness of influenza is one of grave interest, and has been the subject of much controversy. The great rapidity of the spread of epidemics, the vast area they overrun, the fact that they do not follow the lines of human intercourse, the suddenness with which great numbers of the inhabitants of an invaded district or city are seized, the fact that the most complete seclusion from intercourse with affected persons, or even the shutting up of houses, affords in most instances no protection whatever,—all go to show that the disease spreads, in the main, independently of direct contact. This opinion has been almost universally entertained. There is evidence, however, to show that the disease is to some extent contagious; and so convincing have the facts bearing upon this point appeared to some that they have believed it to be propagated entirely by human intercourse. Haygarth¹⁶ declares, as the result of his observations during the epidemics of 1775 and 1782, that the influenza spreads "by the contagion of patients in the distemper;" and Falconer,¹⁷ writing of the epidemic of 1803, says, "I have no doubt that it is contagious in the strictest sense of the word." Watson¹⁸ regards the instances in which the complaint has first broken out in those particular houses of a town at which travellers have arrived from infected places as too numerous to be attributed to mere chance. Very often those dwelling near the invalids are attacked next in the order of time, and when the disease affects a household all do not usually manifest the symptoms at the same time, but one member after another is stricken down with it.

¹⁶ John Haygarth, M.D., F.R.S., On the Manner in which the Influenza of 1775 and 1782 spread by Contagion in Chester and its Neighborhood.

¹⁷ William Falconer, M.D., F.R.S., An Account of the Epidemic Catarrhal Fever, commonly called the Influenza, as it appeared at Bath in the Winter and Spring of the Year 1803, Bath, 1803.

¹⁸ Principles and Practice of Medicine.

In a few rare cases the isolation or seclusion of a community has appeared to give protection, as in cloisters, prisons, garrisons, and the like; at all events, there are instances on record where segregated communities of this kind have escaped attack.

The following observation, conducted under unusual circumstances, establishes the fact that influenza may be brought from an infected city in such a way as to give rise to a localized outbreak in a remote community. Drs. Guitéras and White¹⁹ narrate that, influenza prevailing in Europe, and particularly in Paris and London, an American gentleman in bad health contracted the disease in London, improved, suffered a relapse shortly afterward in Paris, and died there at the end of December, 1879. His body was embalmed and sent home. Following the exposure of the remains of this person to the view of his family in Philadelphia there was an outbreak of influenza with characteristic symptoms, which affected, in the first place, members of that family; afterward, friends living in close intercourse with them; next, the medical attendant of some of them; and finally, the housekeeper and a patient or two of one of the physicians who wrote the paper, the whole number affected in Philadelphia being eighteen at the time of the publication of the account. Subsequently two or three other cases were developed, but the disease did not extend beyond the immediate circle of those in direct communication with the invalids.

¹⁹ John Guitéras, M.D., and J. W. White, M.D., "A Contribution to the History of Influenza, being a Study of a Series of Cases," Philadelphia Medical Times, April 10, 1880.

It was at one time thought that influenza developed at once, without a period of incubation, persons in perfect health being struck down with it as by lightning-stroke. It is, however, now known that a period of incubation, varying from a few hours to several days, and usually without subjective symptoms, exists. Many instances are recorded in which persons coming into an infected city have remained well for one, two, or three days, but have eventually shared the sufferings of those into whose midst they have come. There are cases also in which the period of incubation could not have been less than two or three weeks.

There is no sufficient evidence of a causal relation between influenza and any other epidemic disease. The statement that other prevalent diseases abate in frequency and intensity upon its outbreak is not sustained by well-observed facts. Graves²⁰ holds that those suffering with acute diseases are less liable during the febrile stage, but that they are attacked as convalescence sets in.

²⁰ Clinical Medicine.

The facts in reference to the spread of epidemics of influenza and the course of the disease in infected localities are comprehensible upon no other theory than that of a specific infecting principle as its exciting cause. What this principle may be is not yet known; where it originates is equally unknown; and our knowledge of the influences that from time to time call it into activity and send it forth in definite directions over the earth is no less negative.

So general a disease can only be disseminated by the most general medium, the atmosphere, and its exciting cause must be capable of reproducing itself in that medium, otherwise it would be lost by dispersion in traversing distances measured by the boundaries of continents and oceans. The rapid diffusion of influenza, sweeping over continents in a few weeks at one time, its slow migration, creeping about a city and its environs for months, at another, are to be most easily explained upon the theory of a living miasm capable of being transmitted by the air, and possessing at the same time an independent existence. Such an entity would find certain localities more favorable to its growth, reproduction, and prolonged existence than others. From this point of view influenza is a miasmatic disease. The infecting principle of this disease is also, to a slight extent, capable of being reproduced in or about the human body and transmitted by personal intercourse, as well as conveyed from place to place by the persons or clothing of those affected or those travelling from localities in which the disease prevails. We are thus led to the conclusion that it is also contagious, though feebly so.

CLINICAL HISTORY.—Influenza, in individual cases, presents the greatest variation as regards intensity, from the most trifling indisposition to an illness of the gravest kind, terminating in death. These variations are dependent upon—1st, the previous health of the individual, his age, and the power of resisting depressing influences which he possesses; 2d, the energy and the amount of the specific cause of the disease to which he has been exposed—in other words, the dose of the fever-producing poison; and 3d, the character of the prevailing epidemic.

It is important to observe that cases of very great severity are occasionally encountered during the prevalence of mild epidemics. In every epidemic, on the contrary, a considerable part of the community suffers from influenza in the mildest, or what has been called the rudimentary, form. This is characterized by general malaise, an easily oncoming weariness upon bodily and mental effort, a disinclination for business, some inability to fix the attention, and slight mental confusion; to these nervous disturbances are added catarrhal symptoms, as coryza, sore throat, a tickling cough, and the like; but the indisposition is subfebrile—it does not amount to a fully-developed fever. Other cases present the symptoms of an ordinary attack of acute coryza, laryngitis, bronchitis, pharyngitis, with unusual constitutional disturbance, distressing headache, and pains in the back and limbs. The fever in this class of cases does not range high, yet the patients are ill enough to betake themselves to bed.

In severe cases the onset is usually abrupt. The attack begins with shivering or a chill, or with fits of chilliness alternating with heat. Fever is rapidly established. It is usually moderate; sometimes it reaches a high grade. It shows a tendency to morning remissions. Sensations of chilliness occur; they are called forth by slight changes in the external temperature. They are often followed by flushes of heat, and are, in many cases, attended by annoying sweats. The febrile outbreak is sometimes preceded by intense frontal headache, with pain in the orbits and at the root of the nose. In other cases these pains quickly follow the chill. Sneezing, redness of the eyes and edges of the nostrils, a more or less abundant thin discharge from the nose, and lachrymation, now occur. In some instances there is bleeding from the nose. The throat becomes sore; there is a tickling sensation in the upper air-passages; a dry cough sets in, attended by more or less hoarseness and shortness of breath. The cough is paroxysmal, hard, distressing. It sometimes causes vomiting, like that which occurs in the paroxysms of whooping cough. Chest-pains, stitches in the side, frequent sneezing, loss of the sense of smell and of taste, attend the development of the general catarrhal manifestations.

The fever is attended by great depression, pains in the limbs, loss of appetite, thirst, constipation, and diminished secretion of urine. The pulse is full, but, as a rule, only moderately increased in frequency. There is in many cases slight, or even decided, blueness of the lips and finger-tips. The patient is distressed by restlessness and want of sleep. At the end of four or five days the febrile symptoms decline, at times gradually, oftener rapidly, with copious sweats or spontaneous flux from the bowels. The fever continues, however, when severe complications have taken place, ten or twelve days. The defervescence is marked by an increased flow of sedimentary urine and considerable amelioration of the subjective symptoms. The catarrhal symptoms outlast the fever two or three days, but cough and expectoration may not disappear for some time.

With these symptoms are associated the evidences of functional disturbance of the nervous system. There is remarkable nervous depression; loss of strength and lowness of spirits are combined with mental weakness, or even stupor and delirium. In some cases slight convulsions take place. Cutaneous hyperæsthesia occasionally occurs, and areas of burning pain in the skin are to be met with. Neuralgia, muscle-pain, and aching referred to the bones are very common and often severe.

In other cases abdominal symptoms are prominent, while those referable to the head and chest are less urgent. The disease assumes the guise of a more or less severe catarrh of the gastro-enteric mucous membrane, with disturbance of the functions of the liver. The fever and the peculiar nervous depression are, however, the same. Cases likewise present themselves in which but little of the usual tendency to localization of the catarrhal processes is to be observed; there is fever of varying intensity, with great depression, and simultaneous and equal implication of the head and the organs of the chest and abdomen.

Many writers have sought to arrange the foregoing different forms of influenza in definite categories. It would be a useless task to reproduce their views upon the subject, or even to enumerate the varieties that have been described. In practice, the various described types merge so gradually into each other, and are so modified by the individual peculiarities of the sick, and by the complications which arise in the course of the attack in consequence of such peculiarities or of previously existing diseases or tendencies to special forms of disease, that, in point of fact, particular cases cannot usually be referred to theoretical categories. Hysterical persons and those of a nervous constitution are prone to suffer especially from the peculiar nervous symptoms of influenza. The disease is also modified by the age of the subject of the attack; children manifest in a high degree the signs of cerebral congestion, while old persons are subject in a peculiar manner to dangerous pulmonary complications, and those of a gouty or rheumatic constitution suffer more than others from muscular pains.

The duration of the mildest form of influenza is from two to three days; in well-developed cases without complications convalescence sets in between the fourth and tenth days; while severe cases with complications last much longer, several weeks often elapsing before recovery is complete.

SYMPTOMATOLOGY.—ANALYSIS OF THE SYMPTOMS.—For the purpose of separate consideration it is convenient to take up the symptoms belonging to the fever first, then those of the special catarrh, and finally those more particularly referable to the nervous system; but we encounter in the present state of our knowledge of the pathology of influenza—or our ignorance of its pathology—no little difficulty in deciding under which of these headings particular symptoms are properly to be classed, by reason of the close interdependence of the chief processes of the disease and the anomalies of its phenomena viewed as a whole.

The Fever.—The fever is of the sub-continuous or remittent type, but its range is very irregular. Irregularity of temperature is characteristic of influenza and may assume diagnostic importance.

The intensity of the fever is variable. As a rule, it is moderate or slight; occasionally it is severe. I observed in several cases during the epidemic of 1879 in Philadelphia an evening temperature of only 39° C. (102.2° F.). Da Costa in the same outbreak found the febrile movement not high; the highest temperature he observed was 40° C. (104° F.). Biermer found a temperature of over 39° C. in moderate cases of catarrhal fever, and does not doubt that under certain transient conditions the temperature may reach the height of that of pneumonia or typhus. In weakly persons and the aged the fever is adynamic.

The pulse has no constant characters. Its frequency is moderately increased; it is apt to be less forcible than in health, is generally compressible, sometimes full, often irregular, changing in character in the course of a few hours.

The urine is usually diminished; sometimes its secretion is temporarily suppressed; as a rule, it shows little change, and is rarely, as in other fevers, concentrated and high-colored. It deposits on cooling a sediment of urates, which toward the close of the fever is often very abundant. The defervescence is in many instances attended by a copious secretion of urine. Albumen is not present except as a result of some complication.

At first the skin is hot and dry; later, frequent sweats occur; sweating generally attends the febrile remissions and the defervescence not rarely sets in with copious, acid, ill-smelling sweats. In some cases a tendency to sweat shows itself early and continuous throughout the attack. Sudamina occur in great numbers.

The face is often flushed, and irregular mottlings of the skin, especially upon the neck and chest, have been frequent in some of the epidemics. An outbreak of herpes about the lips is occasionally seen.

Disturbances of the digestive tract are more or less prominent in almost all cases. Only in a rudimentary and sub-febrile form are they absent. In many cases they are such as are usually seen in febrile disorders—namely, loss of appetite, thirst, impaired taste, pasty tongue, tenderness in the epigastrium, and constipation. Nausea and vomiting sometimes usher in the attack. In other cases (the so-called abdominal form) all the above symptoms are more severe, and diarrhoea, colicky pains, and vomiting are superadded. In certain epidemics the intestinal catarrh has shown a tendency to run into dysentery.

The expression of the countenance is changed, in part by the appearance characterizing an ordinary attack of coryza of considerable or great severity, and in part by anxiety and depression. It is pale. Where the pulmonary catarrh is excessive and dyspnoea great the lips become bluish. The facies sometimes suggests that of typhoid fever.

The Catarrh.—A more or less extensive hyperæmia of the mucous membrane of the respiratory tract is invariably present, and may be said to characterize the disease.

There is cold in the head, more severe in most cases than ordinary simple coryza. The eyelids are swollen and reddened, there is lachrymation, sneezing is frequent, and the discharge from the nose is abundant. Epistaxis is not rare. Sore throat, with tickling sensations and difficulty in swallowing, is due to inflammation of the pharynx and neighboring parts. In many instances the catarrhal symptoms are due to a pharyngitis and tonsillitis only, the lower air-passages escaping. Hoarseness is common.

Cough is a prominent symptom. It is apt to be frequent and distressing—sometimes paroxysmal from the beginning of the sickness, almost always so at some period of its course. Its spasmodic character in some of the older epidemics led to the confounding of epidemic catarrhal fever with whooping cough. It is apt to be worse toward evening and at night, but the sick are often tormented day and night by the loud racking cough. It often leads to vomiting, and by its violence and persistence gives rise to pain and soreness in the muscles of respiration (myalgia), and occasionally to hernia. It is at first dry or attended with a scanty muco-serous expectoration; later on the sputa become opaque and muco-purulent, and in consumptive or full-blooded persons or those having mitral disease they are sometimes streaked or mingled with blood. Toward the close of the attack the cough becomes less urgent and loses its spasmodic character. In some epidemics cough is not a prominent symptom, and a few cases are encountered in most epidemics in which well-developed influenza runs its course without unusual, peculiar, or excessive cough. If the cough be due to bronchitis, we find on auscultation the physical signs of that affection. They are of course wanting when it is due simply to laryngo-tracheal irritation. Hence we frequently detect sonorous and sibillant or mucous and subcrepitant râles upon both sides of the chest in the course of the attack, as in non-epidemic acute bronchitis; and, on the other hand, cases occur where the auscultatory signs are but little or not at all altered from those of health. It is scarcely necessary to add that there are no special physical signs that can be regarded as diagnostic of influenza.

Many patients suffer from dyspnoea. Although due in some instances to complications, it occurs with remarkable frequency in those in whom none of the objective signs of any pulmonary lesion can be discovered. It is here of nervous origin. Graves assumes a direct disturbance in the function of the vagus as its cause. This view is sustained by the observation that the dyspnoea is now and then intermittent, or shows rhythmically recurring remissions, which are unattended by alteration of the physical signs. To Biermer it appears more probable that the congestions so common in influenza, not attended by marked physical signs until they lead to oedema, are to be regarded as the cause of the dyspnoea. It varies greatly in intensity. In many patients it goes on to marked oppression, great shortness of breath, precordial pain, and the like. In certain epidemics orthopnoea and suffocative attacks were very common. Stitches in the side and pain under the sternum are observed without appreciable physical signs.

Symptoms Referable to the Nervous System.—Great prostration of muscular strength is a very early symptom, and constitutes, in most epidemics, one of the remarkable features of the disease. Patients from the onset feel extremely weak, and are exhausted by the slightest bodily effort. The ordinary strength is not regained until convalescence is far advanced.

Headache is a constant symptom. Severe frontal pains are scarcely ever absent. They extend across the brow and deeply about the orbits and at the root of the nose, having their seat in the Schneiderian mucous membrane and its prolongations lining the frontal sinuses and the nasal ducts. Sometimes the pain is referred also to the region of the antrum of Highmore and to the Eustachian tube and the middle ear. It occasionally extends over the whole head. Cutaneous hyperæsthesia of the head and neck and stiffness of the neck-muscles are also met with. The headache is often most intense; it lasts commonly till the end of the attack, and may even outlast it. It increases in severity with the fever and mental agitation toward evening. The occurrence of epistaxis affords some relief.

Among the more constant symptoms of influenza are very severe pains in the limbs. Patients experience sensations of soreness and bruising, such as follow the most severe and unaccustomed muscular effort. Dull, tearing, and burning pains are felt sometimes in particular muscles or tendons; sometimes they are diffused over the whole body. Distressing pains of a dragging or boring character in the loins and calves of the legs are complained of. These pains are neither relieved nor aggravated by gentle movement or by moderate pressure. A sense of contraction of the chest and precordial distress also occurs, and stitches in the side (pleurodynia), substernal pain, and pains in the throat and nape of the neck are common. When the attack is severe the patient is usually restless, sleepless, and anxious. Dizziness and a tendency to faint occur on rising, particularly in women. Mild delirium is not uncommon, but the more intense forms are occasionally observed. Active delirium was thought to be a mortal symptom in some of the older epidemics.

The inability to sleep bears no direct relation to the intensity of the fever. It is seen in some cases where fever is slight or even absent.

Somnolent states also occur. Great hebetude and torpor have marked some epidemics. That of 1712 was called the sleepy sickness, by reason of the prevalence of these symptoms.

In grave cases painful muscle-cramps, subsultus tendinum, twitchings of particular muscles, and tremblings of the hands occur.

The mental power is enfeebled, and the acuteness of the special senses is diminished.

COMPLICATIONS AND SEQUELS.—The most important complications of influenza are inflammatory diseases of the lungs. The hyperæmia and intense bronchitis already described as occurring in the severer cases cannot properly be looked upon as complications. They constitute rather essential processes of particular forms of the disease. But capillary bronchitis, catarrhal pneumonia, and less frequently croupous pneumonia, arise as complications in the course of the disease. Satisfactory statistics are wanting, but Biermer estimates that from 5 to 10 per cent. of the whole number of patients suffer from inflammatory lung-complications, and holds that the bloodletting so frequently practised by the older physicians was due to a desire to combat inflammation. The comparative frequency of chest complications in different epidemics varies greatly, but the estimate of Biermer may be accepted as an approximate average.

Owing to the masking of the physical signs in the early stages and the pre-existing pulmonary oedema, it is not always easy to recognize at once the occurrence of capillary bronchitis. This complication is attended with increasing dyspnoea, decided lividity of the face and extremities, and great prostration. Crepitant and subcrepitant râles at the lower portions of the posterior dorsal regions, rapidly spreading to all parts of the chest, without dulness at first and with increased resonance later, instead of the signs of consolidation which are met with in pneumonia, are the signs which attend its appearance.

Catarrhal pneumonia occurs insidiously, with gradual intensification of the bronchitic symptoms about the fourth or fifth day, but it may set in as early as the second day, or much later, during convalescence. It is, as a rule, developed without chill or great increase in the fever.

Old persons and those of feeble constitutions are most liable to the foregoing complications.

Lobar pneumonia is less common. It is a late complication, occurring toward the close of the attack or even when the patient is beginning to get about. It is easily recognized, and differs in no wise from acute lobar pneumonia occurring under other circumstances.

In October, 1880, influenza being prevalent in Philadelphia, both epizoötic and epidemic, but very mild both among horses and men, I attended a medical student who, having had what he regarded as a cold for about a week, had kept at his work without treatment, until, upon the occurrence of a chill followed by grave thoracic symptoms, he was obliged to betake himself to bed. I first saw him the following day in the hospital of the Jefferson College. There were the symptoms of acute lobar pneumonia, with the signs of extensive consolidation of the left lung and pleurisy of the right side. Moreover, there were delirium and jaundice. The urine was non-albuminous. The next evening he died. At the same time many members of the class suffered from influenza, and a careful inquiry into the history of the case of this young gentleman satisfied me that the pneumonia had arisen as a complication in a neglected and moderate severe catarrhal fever. Until the eighth day before his death he was in excellent health. No examination of the body was permitted.

Graves²¹ thought that a kind of paralysis of the lungs, with great oedema, takes place in some cases, and attributed it to an affection of the vagus. It was his conviction "that the poison which produced influenza acted on the nervous system in general, and on the pulmonary nerves in particular, in such a way as to produce symptoms of bronchial irritation and dyspnoea, to which bronchial congestion and inflammation were often superadded."

²¹ Annals of Influenza.

It is certain that localized collapse of the lung often occurs. White and Guitéras attributed the consolidations of the lung to congestive collapse due to enlargement of the tracheal and bronchial glands and "disturbance of the great nervous tract about the root of the lung." They were enabled to satisfy themselves of the existence of glandular enlargement—adenopathie bronchique—in nine of their eighteen cases by percussion practised in the method of M. Geneau de Mussy,²² who was the first to call attention to the importance of percussing the spinous processes of the vertebræ over the course of the trachea. Following this line in the healthy subject, a distinct tubular (high-pitched and slightly tympanitic) sound is elicited by percussion down to the point of bifurcation of the trachea on the level of the fourth dorsal vertebra. Opposite the fifth and downward we get the lower-pitched pulmonary resonance. When the tracheal and bronchial glands are enlarged, the tubular sound over the upper dorsal vertebræ is replaced by dulness, which may contrast sharply, above with the tracheal, and below with the vesicular resonance.

²² Chirurgie médicale, Paris, 1874.

Some well-recognized peculiarities of the so-called pneumonias of influenza give weight to the view that the consolidations are not, in the beginning, pneumonic at all. Thus, we have at first weakness of the vesicular murmur, then its absence; the respiration soon becomes bronchial, without being preceded by dulness or the crepitant râle; the extension of those consolidations from one part of the lung to another is very irregular; the process is more apt to involve both sides than one; the disappearance of the consolidation is frequently very rapid.

The relations of cause and effect between collapse and catarrhal pneumonia are so close that it is not difficult to see how the condition spoken of may lead to secondary lobular or catarrhal pneumonia. In truth, this is a frequent result of collapse from any cause.

White and Guitéras do not adduce any post-mortem facts in support of their theory. Peacock, however, observed in the epidemic of 1847 softening and enlargement of the bronchial glands in several cases, and in one instance where there was no antecedent disease of the lungs, and where the physical signs corresponded to some extent with those of the cases upon which White and Guitéras base their views.

Gangrene of the lungs must be named as one of the less common complications.

These complications are the chief cause of the danger of influenza in the aged, the debilitated, and those suffering from previous disease of the thoracic organs.

Pleurisy is rare except where there is coexisting inflammation of the lungs. It may be associated with pericarditis. In old persons serous effusions into the pleural sac are now and then encountered.

Troublesome laryngitis and chronic bronchitis may follow the attack. In consequence of the extension of the catarrhal processes along the Eustachian tube an actual inflammation of the middle ear is, in rare instances, set up. Parotitis with salivation sometimes occurs, likewise aphthous inflammations of the mouth.

Herpes labialis occasionally occurs toward the end of the attack; it is then a favorable indication.

Phthisis may be developed in consequence of an attack of influenza, and if phthisis be already established it is apt to run a more rapid course. Emphysematous affections are aggravated; diseases of the heart are unfavorably influenced; chronic nervous affections are made worse, and, in particular, neuralgias are aggravated. Old neuralgias, that have long ceased to give trouble, occasionally reappear during the convalescence.

Persons subject to latent or chronic Bright's disease are especially liable to the more serious manifestations of influenza. The fatal termination of such cases not unfrequently occurs in consequence of an attack.

Many of the older observers speak of the intermittent character of influenza in certain epidemics, and its tendency to run into intermittents, particularly of a certain type, during convalescence. This has not been observed in the outbreaks of later years, and it is probable that in such instances an endemic malaria has modified the epidemic catarrhal fever, or the former has broken out as the latter passed away.

Pregnant women are in danger of aborting.

PATHOLOGY.—Our knowledge of the pathology of influenza is as yet very imperfect. Biermer has described it as the sum of a series of catarrhal manifestations developed under a common epidemic influence. The close association of the various local affections arises from their almost simultaneous occurrence as results of primary pathological processes common to them all. Each of the three groups of symptoms which make up the clinical picture of the disease—namely, the fever, the catarrh, and the symptoms referable to the nervous system—constitutes a distinct factor of influenza, and is a direct outcome of the action of the infecting principle. There is no constant interdependence among these groups, either in the order of their succession or in their intensity. Thus, while all three groups are commonly present from the beginning of the attack, any one of them may be the first to appear or have an intensity out of all proportion to each of the others. The fever is not a result of the catarrhal inflammation, nor are the nervous symptoms the result of both the others. They all spring directly from the action of the same cause.

This view is at variance with the opinion—based upon the fact that ordinary acute local inflammatory diseases, tonsillitis, bronchitis, and the like, sometimes run their course in a similar way to influenza, with fever, nervous depression, and a serious sense of illness—that influenza is a simple epidemic catarrhal inflammation.

The sudden onset of influenza, its not infrequent abrupt termination, which suggests crisis, its unsparing seizure of great numbers of the population, the severity of the nervous symptoms, and the amount of laryngo-bronchial irritation, often out of measure with the lesions of the mucous membranes,—all point to the action of a morbid agent affecting the body at large. The severity of the symptoms also, in many cases, is much greater than in similar acute non-specific local affections, while the complications, and in particular the recrudescence of fading neuralgias and the tendency to abortion, and the sequels, as cough, weakness, headaches, flying pains, which often remain long after convalescence, are evidences of its belonging to the group of infectious diseases rather than to that of simple acute inflammatory diseases.