Volume 1 — GENERAL PATHOLOGY. (continued 5)

Retardation of the flow of blood through the veins is manifest during the collapse of epidemic cholera. On pressing the blood back in a vein upon the hand, for example, and then lifting the finger, instead of the movement being, as in health, too swift to be seen, it is so slow as to be easily followed.

Capillary movement may be estimated in a similar manner. If it be very sluggish, pressure upon the cheek, forehead, or hand will cause a pallor which remains for some seconds, instead of disappearing at once when the pressure is withdrawn. This is, it may be noticed, entirely different from the pitting upon pressure, without much if any change of color, in local oedema or general anasarcous effusion. The tache méningitique of Trousseau is a pink or rose-red line left for a time after drawing the finger across the forehead or abdomen in cases of acute hydrocephalus (tubercular meningitis).

Respiration must be watched carefully in all cases of disease. Normally, in the adult, while at rest, from 16 to 18 respiratory movements occur in each minute. The number is somewhat greater in women, and is considerably increased in children, at birth being about 40 in the minute. Men breathe most by the diaphragm; in women there is a greater lifting of the ribs. In either sex a disorder attended by pain in breathing may modify this proportion. If pleurisy, for example, be present, the ribs will be but slightly lifted, abdominal breathing taking predominance. When peritonitis makes every movement of the abdomen painful, costal respiration is maintained almost alone. Likewise, a unilateral pleurisy or pneumonia will check the respiration on the affected side, with an increased movement on the sound side. This difference is less manifest to the eye than to the ear in auscultation. In all febrile affections respiration is hurried proportionately with the pulse, unless some complicating local disorder disturbs the relation.

Dyspnoea may be produced by many different causes, whose possibility must be remembered in its interpretation as a means of diagnosis. In asthma violent efforts are made to compel the entrance of air into the lungs by the intercostal muscles and diaphragm, aided by all the accessory muscles of respiration, including the sterno-cleido-mastoid and others of the neck. Expansion of the nostrils may occur in sympathy with these efforts. Yet the amount of resistance may be shown by a partial sinking-in of the lower ribs, as well as by the patient's distress. These last signs are sometimes very marked in the collapse of one or both lungs now and then occurring in whooping cough.

Croup induces a similar struggle for breath, although the obstruction is differently located. Early in the croupal attack a hoarse sound may accompany each inspiration and expiration. Later, when the danger to life from apnoea becomes more imminent, a hissing or whistling sound succeeds. This last-mentioned kind of sound results temporarily, also, from the spasmodic obstruction to breathing in laryngismus stridulus.

Besides the affections of the lungs which impede respiration (as pneumonia, hydrothorax, etc.), we may have dyspnoea induced by extra-pulmonary causes, such as dilatation of the heart, aneurism of the aorta, mediastinal cancer, pleuritic effusion; also by abdominal dropsy, extreme elephantiasis, etc. Mention need hardly be made here of respiratory obstruction from defective or injurious qualities of the air, threatening or producing asphyxia.

Sighing respiration takes place in heart disease not infrequently. A peculiar modification of the breathing movements has been associated especially with fatty degeneration of the heart. From the distinguished authors who first described it this is called the Cheyne-Stokes respiration. Intervals of suspension of breathing occur, after which short, shallow inspirations begin, and gradually increase for a time in depth; then they grow shorter and shallower again, until apnoea is reached. Such a cycle may occupy from half a minute to a minute and a half, with from fifteen to thirty increasing and decreasing respirations in all. It has been shown by several observers that this type of respiration is not peculiar to fatty degeneration of the heart. It has been met with in cases of cardiac dilatation, aortic atheroma, cerebral hemorrhage, tubercular meningitis, and uræmia.

Sometimes a kind of dyspnoea common in advanced disease of the heart, especially in mitral lesion with dilatation, has been confounded with this. Here the breathing is constantly labored (orthopnoea); but the patient from time to time dozes off into an imperfect sleep, in which the breathing almost entirely ceases. Then he is awakened with a start of distress, perhaps out of a painful dream. This succession of dozing apnoea and waking dyspnoea belongs to a late stage of heart disease, and usually ends in death.

Stertorous respiration is familiar in apoplectic coma, as well as in that of brain compression from injury or from opium or alcoholic narcotism. In uræmic coma true stertor is less apt to be observed; sometimes the respiration in this condition has a hissing sound.

Along with the movements of respiration we may notice that the breath is hot and has a heavy odor in the early stages of all febrile disorders. Disagreeable breath is common, however, in persons not ill, from bad teeth or from indigestion. It is worst of all, putrid, in gangrene of the lung. Certain cases of chronic or subacute bronchitis (as well as of ozæna) also have very offensive breath. Coldness of the breath is a very bad sign; it is observed sometimes before death in the collapse of cholera.

Hiccough (singultus) is a spasmodic affection of the diaphragm. It is innocent, though annoying, in most cases, resulting from indigestion or from nervous disorder; in children, occasionally, from long crying. When it takes place in cases of general prostration it betokens threatening depression or exhaustion of vital energy.

The voice is mostly altered by serious disease. It may be feeble and whispering, from debility; hoarse, from laryngeal inflammation and tumefaction; thick, from cerebral oppression; lost (aphonia), in some cases of chronic laryngitis and in paralysis of the vocal muscles. The manner of articulating words is often changed in disorders of the nervous system. A marked example of this is the monotonous scanning speech of cerebro-spinal sclerosis.

Cough is an extremely variable symptom, always to be understood in connection with the attendant circumstances. Usually, however, the character of the cough itself is more or less distinctive. A dry, hard cough may be merely sympathetic or nervous, or it may belong to the first stage of acute bronchitis. A hacking cough, with little expectoration, is not infrequently observed for a time in incipient phthisis. Pneumonia has, if any, a short and rather sharp cough. Progressing bronchitis is recognized by the deepening and greater or less loosening of the cough. In advanced phthisis there are distressing spells of deep, laborious coughing, especially in the night or in the morning after sleep. Croup is known (whether sporadic or in the form of laryngeal diphtheria) by the barking cough of the early stage and its whistling character toward the fatal end. Nearly the same sort of hissing or whistling sound in breathing has been mentioned already as occurring in laryngismus stridulus. Paroxysms of coughing, with or without whooping, are pathognomonic of pertussis.

Expectoration often affords important signs. Briefly, it may suffice to say here that it is mucous, whitish, or colorless in early bronchitis; more or less yellowish and muco-purulent in severe and protracted bronchitis; rusty, from admingling of the coloring matter of blood, in pneumonia, early and middle stages; bloody and muco-purulent in early and of heavy roundish (nummular) masses in late pulmonary phthisis; putrid, rotten, in gangrene of the lung.

Continuing our survey of obvious symptoms, we must now take account of the conditions of the general surface of the body. Temperature is of great consequence. Most precisely determinable by the thermometer, the touch, when educated, will give very useful indications of its changes. It is difficult, and not commonly desirable, to separate variations of moisture from those of temperature. Reserving for another place the special consideration of medical thermometry, it may be here said that the skin is hot and dry in the typical condition of fever, whatever its special associations. Heat and moisture of the skin are more often met with together in the fever of acute articular rheumatism than in any other affection. As a rule, perspiration lessens febrile heat. Copious (colliquative) sweating is habitual in many wasting diseases, notable in pulmonary phthisis. It is then a sign of great general relaxation of the system.

Coldness of the surface attends prostration, either from temporary collapse or from positive exhaustion. The skin is perceptibly cold in the algid stage of cholera. It may be so in very severe cases of sporadic cholera morbus. In the chill of intermittent, while the patient has the subjective sensation of coldness, his temperature is seldom reduced, and is often higher than natural, although lower than during the febrile exacerbation.

The color of the skin is pallid in anæmia, phthisis, dropsy, etc., and in syncope; ashen or livid in cholera collapse and in the cold stage of pernicious malarial fever; yellow in jaundice, remittent, and yellow fever; sallow in chlorosis, cancer, and chronic dyspepsia; purple, almost black (especially the lips and ends of the fingers), in asphyxia; dark, as if stained with ink, after long use of nitrate of silver; bronzed in Addison's disease; bright red in scarlet fever, etc. The eruptions of this and other exanthemata, and of the different cutaneous diseases, will be best considered in the special articles treating them of in this work.

Odor is perceptible and peculiar (though not easily described) in some bad cases of typhus fever and of small-pox; less often in aggravated chlorosis. Lunatics and paralytics (especially when assembled together in institutions) often give off a noticeable smell. Most distinct, however, is the cadaverous odor, sometimes perceptible for hours before death. Corroborative of this, in summer, is the flocking of flies around the bed of a dying patient. In a hospital ward this selection amongst a number of patients may be quite observable.

Emphysema, from the presence of air in the connective tissue under the skin, is rarely met with except as the consequence of an injury or of local gangrene.

Oedema is local watery effusion, which may have various causes and significance. Anasarca must have a general causation, either connected with the state of the blood or with disorder of the heart, kidneys, or liver, or of more than one of those organs at once. Pitting on pressure is the sign of watery effusion. Soft crackling under the touch distinguishes emphysema. A firm enlargement of the surface of the face and upper part of the body occurs in myxoedema.

Swellings of all kind must be carefully observed, and their nature inquired into—whether they be inflammatory or other chronic enlargements of joints, tumors, fibrous, fatty, or cancerous, aneurisms, hernial protrusions, or of any other character. In protracted disease of the liver (cirrhosis) it is not uncommon to find the superficial abdominal veins dilated and tortuous.

Abdominal enlargement may result from adipose accumulation (obesity), distension of the bowels with wind (meteorism), ascites, ovarian cysts, cancerous or other tumors, aneurism of the aorta, abscess, retention of urine, or pregnancy. By the methods of physical diagnosis, along with careful inquiry into the history of each case, we are to make out the distinctions amongst these different conditions.

Emaciation always marks either defect of nutrition or morbid excess of tissue-waste. It is counterfeited in the sudden collapse of malignant cholera, and exaggerated in appearance during the analogous condition of cholera infantum. On recovery from these states, especially the latter, roundness and fulness of the face and limbs may return much too soon for the actual restoration of fat and flesh. A young child may be plump and chubby to-day, seemingly wasted with acute illness to-morrow, and, if soon relieved, the next day almost as rotund as ever.

Continued diarrhoea, phthisis pulmonalis, mesenteric disease, cancer, and aneurism of the aorta are among the most frequent causes of great emaciation. Sometimes, as in progressive pernicious anæmia, we are struck with the comparatively slight degree of wasting of the body while the disease is advancing toward death.

In myxoedema there is a swelling or general enlargement, especially of the upper portions of the trunk. This is not anasarcous, but depends upon a morbid change in the connective tissue throughout the body.

Articular enlargements may be (particularly in the knee in children) scrofulous, or gouty (in the smaller joints), rheumatic, with evidences of inflammation, acute or chronic; or, what is not well named, rheumatoid arthritis. In this last affection there is a gradual swelling and stiffening, with but little inflammation, of several, sometimes all, the joints of the extremities. Locomotor ataxia is in some cases attended by a degenerative alteration in one or more of the larger joints.

The limbs may furnish to the eye many expressive signs of disease or disability. In the listlessness of one arm and hand, while the other can perform various movements, we see reason to suspect hemiplegia. If the fingers are rigidly contracted, as well as powerless, we have this diagnosis confirmed, whether the rigidity be early or late in its stage. We must then look for a similar condition of the lower extremity on the same side. Paraplegia and general paralysis have their more extended (bilateral) indications in like manner. Characteristic also are the wrist-drop, from paralysis of the extensors of the hand, in lead-palsy; weakness or incapacity of the flexors and extensors in writer's cramp; the hand fixed helplessly in the position for writing in paralysis agitans (advanced stage); the main en griffe, with shrunken muscles and drawn tendons, of progressive muscular atrophy (wasting palsy). In the legs at first and chiefly, but in time also in the arms, increase of bulk with loss of power in the muscles shows the existence of pseudo-hypertrophic muscular paralysis.

Gouty fingers have their joints not only swollen, but distorted by deposits of urates and carbonates. Clubbed finger-ends, in the adult, are seen mostly, with incurvation of the nails, in advancing consumption. The nails are sometimes striated after attacks of gout, the lines disappearing gradually during the interval. In many acute diseases, transverse ridges are noticeable on the nails, marking the date when their growth was arrested and subsequently resumed. These are specially remarkable after attacks of relapsing fever.

A tendency to dropsical effusion is generally first shown, besides a puffiness of the face, in the feet and ankles, the shoe or slipper marking off the enlargement above its margin. Often this has no other cause than debility, with a watery condition of the blood. Varicose veins, with old and resultant ulcers, are also among the possible things to be found in examination of the legs and feet.

Movements of the hands are incessant and jerking in chorea; perpetually trembling in delirium tremens, and often in one arm and hand only, in paralysis agitans; with tremor, seen in voluntary motions alone, in multiple cerebro-spinal sclerosis. More unusual is the rhythmical closing and opening of the hand, successively, of athetosis.

In the walk of patients able to be upon their feet there may be much significance. A hemiplegic subject will circumduct the feeble limb after the other; one suffering with paraplegia will shuffle the feet slowly along the floor; the hysterical paralytic drags the lame limb behind the other; the patient with spastic spinal paralysis rises on his toes in walking, with his legs held close together; the shaking paralytic rather trots forward, with the body bent; and the subject of locomotor ataxia lifts his feet and kicks out forward or sideways, then bringing down the heels with a stamp at each step. In progressive muscular atrophy and advanced pseudo-hypertrophic muscular paralysis a waddling or rolling gait is seen. Choreic patients are very irregular in their walk, as in all other movements. Hip disease (coxalgia) shows itself in a child by its lifting the pelvis and limb of the affected side and bending the knee, so as to touch only the toes to the ground. Club-foot and other deformities require no description in this place.

Sensibility of the extremities and of other parts of the surface of the body needs to be examined into, with all its possible variations (hyperæsthesia, anæsthesia, analgesiæ, etc.), especially when the nervous apparatus is for any reason supposed to be involved. Motions of an unusual character must likewise be carefully noticed. "Westphal's symptom" is regarded as having considerable diagnostic value. It is otherwise called the tendon-reflex, with its modifications. When a person in health is seated with one leg crossed over the other or with the legs dangling over the edge of a high bench or table, and a sudden blow is struck upon the tendon of the patella, the leg and foot will be spontaneously jerked forward. In locomotor ataxia, even from an early period, this tendon-reflex is abolished. In spastic spinal paralysis (lateral spinal sclerosis) it is exaggerated. Quite analogous to this is the ankle-clonus. This is obtained by firmly flexing the foot and then tapping sharply upon the tendo Achillis. The foot is then involuntarily extended and flexed several times in succession. There is more doubt in regard to the associations of this symptom than as to the knee movement, but it has been clinically shown to be exaggerated in spastic spinal paralysis.

At our first acquaintance with a case of disease, while making inquiry into its nature, the genital organs must not be forgotten. Not that we need always make examination of them, but any pointing in symptoms toward them must be borne in mind, so as to guide us in or toward further procedures in diagnosis. In making, in obscure cases, a diagnosis by exclusion, we are sometimes driven to a scrutiny of the genital system.

We have now, however incompletely, touched upon the greater number of obvious signs or symptoms which a view of a patient would furnish without making minute inquiry of himself or others concerning his or their knowledge of the illness. Such are the objective signs of disease, which must be still more exactly and extensively discerned and understood by means of the processes of physical and instrumental diagnosis. But the subjective symptoms also, and all those observed and described by the patient and his or her friends, must receive very careful attention. Much practical skill may be shown by the kind of questions asked and the use made of the answers given.

First, as to the alimentary apparatus:

Taste is very commonly altered in disease, being sour in indigestion, bitter in disorders of the liver, saltish in hæmoptysis, rotten in gangrene of the lungs.

Dryness of the mouth is the rule in fevers. Sometimes the saliva is viscid and adherent. Increased flow or salivation was formerly frequent in practice under large doses of mercurials. Jaborandi or its alkaloid pilocarpin will generally produce it. Iodide of potassium occasionally has the same effect in less degree.

Loss of appetite nearly always attends serious diseases of any kind. Excessive craving for food (bulimia) is rare. Tapeworm accounts for it in some instances. Desire for strange articles of food, as slate-pencils, ashes, etc., is met with in some instances of chlorosis and of hysteria. A return of natural appetite is one of the best signs toward the close of any acute attack of illness.

Thirst is seldom absent in fever. It is also usually present in the state of collapse, as from cholera, pernicious intermittent, or the shock of severe (especially railroad) injuries.

Dysphagia or difficulty of swallowing may result from simple debility, as in the moribund state; inflammation of the fauces, tonsils, or pharynx; stricture of the oesophagus; obstruction by a foreign body or by a cancerous or aneurismal tumor; retro-pharyngeal abscess; paralysis of the muscles of the throat, such as sometimes follows diphtheria. Soreness of the throat is present in some, but not in all of these examples of dysphagia, being most marked in the inflammatory condition of pharyngitis, tonsillitis, scarlet fever, and diphtheria. Ulceration of the throat should always be carefully looked for, and if present investigated to ascertain whether it is simple, diphtheritic, or syphilitic. We must be careful not to mistake a mere local accumulation of mucus, or aphthous vesicle, or the curd-like formation of thrush or muguet, either for ulceration or pseudo-membranous deposit. Aphthæ and thrush are most frequently met with in children, though small aphthous ulcers frequently appear toward the close of wasting, and especially cancerous, affections. If there be a doubt, pass a moistened hair pencil lightly over the apparent deposit, or allow the patient to gargle the throat with water, and then re-inspect it.

Many causes may produce nausea and vomiting, which almost always occur together; that is, vomiting rarely takes place without previous nausea, although the latter may exist without the former. In the manner of vomiting there are some differences more or less characteristic, as the distressing retching of sea-sickness and of tartar emetic or other irritant poisoning, and the spasmodic out-spurting of rice-water fluid in malignant cholera. The matter vomited is often very important in diagnosis. In mere indigestion the food taken is apt to come up, and the same may happen in flatulent colic. When the liver is involved, as in bilious colic, bile also is ejected. Nothing peculiar exists in the ejecta of morning sickness in pregnancy. The ejecta contain mucus in gastritis, blood in ulcer and in cancer of the stomach, stercoraceous material in obstruction of the bowels, black vomit in bad cases of yellow fever. Hysterical vomiting sometimes closely imitates the latter in appearance. Other affections attended by vomiting are cholera morbus, remittent fever, brain disease, Bright's disease of the kidney, etc.

Spitting blood may be either hæmatemesis or hæmoptysis proper. If the former, nausea generally precedes the ejection of the blood by vomiting, and it is apt to be mingled with food partly digested. It is coughed up, bright red and frothy usually, when coming from the lungs or bronchial tubes. But blood may proceed from the gums or throat, or may run back through the posterior nares from the nose, and then it gives alarm by seeming to proceed from the chest. It is necessary to inquire very particularly into all such possibilities in every case of hemorrhage.

Between vomiting of blood from ulcer and from cancer of the stomach we have mostly these distinctions: in ulcer it follows soon after taking food, in cancer (this being generally at the pylorus), an hour or more after eating; ulcer is attended also by tenderness on pressure at a certain spot over the stomach, without tumor; cancer presents a tumor, with much less marked tenderness on pressure. By aid of the microscope in examination of the matter vomited this diagnosis may be completed.

Constipation is an exceedingly frequent symptom under many and diverse circumstances. Pathologically, we account for it in several ways: 1, torpor of the muscular coat of the intestinal canal; 2, deficiency of secretion in the glands of the bowels and in the liver; 3, imperfect innervation of the abdominal organs; 4, mechanical obstruction, as by a foreign body, intussusception, strangulated hernia, cancerous or other tumor, stricture of the rectum, etc. Dyspeptic persons are ordinarily constipated. So are almost all patients at the beginning of attacks of measles, scarlet fever, small-pox, and other acute febrile maladies. Typhoid fever is scarcely an exception to this; although the bowels in that affection become loose after a few days, they seldom are so at the very beginning of the attack. Sea-sickness is commonly accompanied by total or nearly total inaction of the bowels, the secretion of the intestinal glands being almost null, often for many days together. Torpor of the brain is sometimes attended by marked constipation. The latter may be a contributing cause of the former, as in certain severe cases of scarlet fever, in which threatening coma may be relieved by active purgation. We must not, however, occupy space here by attempting to enumerate the many conditions under which constipation may present itself as a symptom.

Almost as various are the associations of the opposite state of the bowels, diarrhoea. Excessive or abnormally frequent discharges from the bowels may be either fecal, bilious, mucous, membranous, purulent, bloody, fatty, or watery, and they may occur with or without pain and straining (tenesmus).

If, with frequent disposition to pass something, only small quantities of bloody mucus escape, with pain and bearing down, we recognize dysentery. When, instead, a large quantity of colorless fluid, with or without floating flakes (rice-water), comes from the bowels at short intervals, with vomiting of the same sort of material, we suspect epidemic cholera, and must inquire for corroborative or corrective indications in reference to that suspicion. Very bad cases of cholera morbus also may, at a late stage, present this symptom. So may exceptional cases of pernicious malarial fever. The diarrhoea of typhoid fever exhibits usually liquid stools of a brownish color (gutter-water passages). Occasionally, hemorrhage from the bowels adds to the danger of this fever, as well as to that of malarial remittent fever. In phthisis pulmonalis, at a late stage, colliquative diarrhoea, like colliquative perspirations, shows the breaking up of the system by excessive waste. Very foul, offensive discharges from the bowels may always be understood as showing that in the alimentary canal, whether originating there or in the blood, morbid changes have been going on. The indication is to promote the elimination of such material as soon and as thoroughly as possible.

Clayey stools show absence or deficiency of bile in the intestines, whether from its non-secretion by the liver or from obstruction to its entrance by a gall-stone in the common gall-duct. Green stools are not uncommon in sick children. The cause of the color has been much disputed. Probably it depends chiefly on a modification of the bile-pigment, with some admixture of altered blood. When mercurials have been taken sulphide of mercury may give a green color to the discharges.

Blood, nearly or quite unmixed, coming from the bowels, may have its origin in internal hemorrhoids, intestinal ulceration, cancer of the rectum, intussusception, rupture of an aneurism, typhoid or yellow fever, or vicarious menstruation.

Pus is discharged per anum in cases of dysenteric or other ulceration of the bowel; also when an abscess occurring in any part of the abdomen (most frequently hepatic) opens into the intestine. Pseudo-membranous discharges, shreds or other fragments of fibrinous material, appear sometimes in what may be called diphtheritic dysentery. Tubular casts are occasionally seen (diarrhoea tubularis), which, however, are most likely to consist of thickened and accumulated mucus. Fatty discharges from the bowels are rare. Authors report observation of them in cases of disease of the liver or pancreas, as well as in phthisis, typhoid fever, diabetes mellitus, cholera, and tubercular enteritis of children.

Lientery is the term applied when imperfectly changed food appears in the stools. It shows, of course, great deficiency in the process of digestion.

Urination affords symptoms often of extreme consequence in disease. Suppression of urine is one of the most alarming of signs; an approximation to it only is likely to be met with in cholera, a late stage of scarlet fever, typhus or typhoid fever, in acute yellow atrophy of the liver, and in advanced kidney disease. Careful examination of the abdomen, by inspection, palpation, and percussion, as well as by inquiry of attendants, is needful in all cases of fever or other disorders with delirium or stupor, to ascertain the presence or absence of retention of urine. Dysuria—i.e. difficult urination, strangury—may have several causes. Cantharides, absorbed from a blister, may produce it temporarily. The more continuous states which cause it are—stricture of the urethra, enlargement of the prostate gland, and calculus in the bladder. In stricture, when the patient can pass water, it is apt to be in a twisted stream. Dribbling often occurs when the prostate is enlarged. When a stone is present the stream may flow naturally for a time and then suddenly cease from obstruction at the outlet of the bladder. Enuresis, incontinence of urine, is often very troublesome in children; its diagnosis presents no difficulty.

Diabetes properly means simply excessive flow of urine. It may be attended by no change in the secretion except dilution of its solids (diabetes insipidus), as in certain nervous cases or after very large imbibition of fluids. More serious is diabetes mellitus, in which large amounts of sugar are found in the urine.

Variations in the quantity and in the composition and solid ingredients of the urine, as ascertained by aid of chemical analysis and the microscope, will be fully considered in other portions in this work.

Menstruation in the female requires scrutiny in every case of deviation from health. Its abnormities will be elsewhere treated of. The subject of the signs of pregnancy belongs of course to treatises on Obstetrics.

Pain is one of the most important of the signs of disease. We must always examine its character, location, and associations. As to character, that of pleurisy is sharp and cutting, increased by deep breathing or coughing. In pneumonia and in myalgia it is dull or aching. Rheumatic joints or muscles suffer a gnawing, tearing pain. In neuralgia it is darting, shooting, lancinating; and the last of these expressions is often applied to the pains of cancer. Griping pains occur in colic, and bearing-down pains in dysentery, as well as in the second stage of labor. Besides these varieties we have the pulsating pain of an acute external inflammation, as of the hand, especially before suppuration has occurred; the burning and smarting of erysipelas; and the stinging, nettling sensations (formication) of urticaria.

Tenderness on pressure is significant either of local inflammation, whose other signs are then to be discerned, or of non-inflammatory hyperæsthesia. The origin of the latter may require careful examination of various organs for its discovery. If pain is relieved by pressure, we may be sure of the absence of severe acute local inflammation.

Not infrequently the seat of disease may be at some distance from that of pain, as in the familiar instances of pain at the top of the head in uterine derangement; in the glans penis from calculus in the bladder; in the knee from hip-joint disease; under the shoulder-blade in liver disorder; about the heart or between the shoulders from dyspepsia.

Anæsthesia, loss of sensibility, has much value as a symptom in neurotic affections, as paralysis, etc. Its discussion will find place in connection with diseases of the Nervous System in other portions of this work.

As an example of the diversified associations of pain, cephalalgia (headache) may be mentioned as having at least the following possible causes: congestion of the brain, neuralgia, rheumatism of the scalp, uterine irritation, disease of the kidneys, early stage of remittent, typhoid, or yellow fever, alcoholic intoxication, chronic disease of the brain.

Abdominal pain may, in like manner, be traced, in different cases, to many morbid conditions, such as flatulent colic, lead colic, neuralgia or rheumatism of the bowels, intestinal obstruction, dysentery, passage of a gall-stone or of a nephritic calculus through one or the other duct respectively; cancer, aneurism of the aorta, caries of the spine; in the female, dysmenorrhoea, metralgia or ovaralgia—i.e. neuralgia of the uterus or ovaries.

Similar diversity in the origins of pain might, but for want of space, be pointed out in morbid states of the contents of the chest and of other parts of the body.

Subjective symptoms often affect the special senses.

Taste and touch have been already referred to. Of sight we may have photophobia, connected with exaggerated sensibility of the retina or of the brain; muscæ volitantes, specks, rings, or chains of spots from floating semi-opaque particles in the vitreous humor; diplopia, double vision; hemiopia, seeing only half of an object at a time; amblyopia, indistinctness of vision of all objects.

Hearing is affected, besides all possible degrees of deafness, with the subjective sensations of ringing, whistling, or roaring sounds—tinnitus aurium. One form of this (as I conclude from observation in my own ears) depends upon spasmodic vibration of the tensor tympani or stapedius muscle. Sometimes the seat of the sensation is in the auditory nervous apparatus proper. It has, not seldom, a marked connection with brain-exhaustion. An attack of Menière's disease (labyrinthine vertigo) is often preceded by it. No constant signification, however, can be attached to aural tinnitus. Large doses of quinine or of salicylic acid will occasion it in many patients.

Very briefly, deafness may be here disposed of by mentioning that, in greater or less degree, it may be produced by accumulated wax in the ear; obstruction of the Eustachian tube; thickness of the membrana tympani; perforation of that membrane; mucus or pus in the middle ear; disease of the ossicles of the ear; paralysis of the auditory nerve; typhus or typhoid fever; excessive doses of quinine or salicylic acid.

Vertigo is chiefly of two kinds, dizziness or giddiness (swimming in the head), and reeling vertigo, or a disposition to fall or turn to one side or the other. Giddiness is produced by running or whirling many times in a circle, or, in some persons, by swinging rapidly or sailing. Reeling vertigo is mostly observed in connection with disorder of the brain or of the labyrinth of the ear (Menière's disease). Dizziness, with nausea, is common as a symptom of cholæmia (cholesteræmia of Flint) in what is popularly called a bilious attack.

Delirium is present in many acute disorders, and not infrequently at a late stage in pulmonary phthisis. Its special study will be taken up in connection with the special articles upon these affections.

Coma, or stupor, is met with chiefly in the following morbid states: severe typhus or typhoid fevers; malignant scarlet fever; small-pox; rarely in measles; pernicious malarial fever; uræmia; apoplexy; opiate narcotism, or that from chloral or alcoholic intoxication; asphyxia from inhaling carbonic acid gas, ether, chloroform, etc.; fracture of the skull with compression of the brain.

For an account of aphasia and other morbid psychological manifestations the reader is referred to the articles on Aphasia, Insanity, Hysteria, etc. in this work.

Physical and Instrumental Diagnosis will be treated in connection with those diseases in which they have special importance.

PROGNOSIS.

The elements of medical prognosis are essentially involved in diagnosis. Our ability to anticipate the mode of progress, duration, termination, and results of any case of illness depends upon our knowledge—1, of the nature of the malady, with its tendencies toward death, self-limitation, or indefinite continuance; 2, the soundness or imperfection of the patient's constitution, with or without special predispositions or the consequences of previous ailments; 3, the present state of his system as to the performance of the general functions, his strength, and vital resistance or persistence; 4, the probable modifying influences of medical treatment, and also those of situation, surroundings, and nursing—i.e. the care of those attending to the patient during the absence of the physician and having the duty of carrying out his directions.

1. As to the nature of the malady. While every sickness must be supposed to encroach somewhat upon the vital energy of its subject, very few diseases (leaving aside deadly poisons and surgical injuries) are, ab initio, certainly fatal. Hydrophobia (rabies canina) has been, until latterly, regarded as incurable, and always mortal within a few days or a week or two. A few cases have, during the last few years, been reported as cured, but the diagnosis of these continues to be somewhat doubtful.

Cancer exhibits a tendency to extend its destructive malnutrition so as to render death inevitable unless it can be removed early and completely, or unless the morbid process can be arrested in some manner not yet known. Remedies, such as condurango and Chian turpentine, which furnished hope of such an effect, have, after prolonged trial, been abandoned as not justifying the confidence of the profession.

Tubercular phthisis was once considered to be almost necessarily a fatal disease, although with a very indefinite period of duration. Under improved hygienic management, with mild palliatives and recuperative medication, a not inconsiderable minority of cases now end in recovery. This term may be properly applied when, with cicatrization of a cavity or cavities in the lungs, no more tubercle is deposited and lung-substance enough is left for good respiration, even although the structurally changed portions of pulmonary tissue do not undergo entire repair.

Tubercular meningitis is a nearly always incurable affection. Yet a few instances of lasting recovery have been reported where the diagnosis was as certain as it can be in that disease in the absence of post-mortem examination. A child attended by myself, in whom the symptoms had been of the most unfavorable kind, became apparently quite well, and continued so for a month. Then it was attacked suddenly with convulsions, which were almost unremitting until it died within a day or two.

Gangrene of the lung is very seldom recovered from, but, unless the diagnosis from examination of putrescent sputa has been at fault, there have been cases in which, with the limited destruction of the affected lung, it was not fatal.

Pseudo-membranous croup destroys life in the majority, but not in nearly all the cases of its occurrence. It is most likely to end in death when distinctly a part of an attack of epidemic or endemic diphtheria.

Valvular heart lesions were formerly regarded as incurable, in the sense of restoration of the normal condition and action of the valves impaired, yet not incompatible with years of life. This restoration certainly very seldom takes place. But the experience of many close observers leads to caution in anticipation of necessary and permanent disability of the heart because of murmurs, or even functional disturbances, seeming to prove either aortic or mitral insufficiency or stenosis.

Aneurism of the aorta is very seldom recovered from, but, besides a variable duration, whose period can almost never be anticipated with exactness, there appear to have been some cases of disappearance, or at least prolonged quiescence, of the tumor and of its morbid effects.

Yellow atrophy of the liver is one of the disorders most rarely ending otherwise than in death.

With a course altogether indefinite in time, there appears to be a tendency to exhaust vital energy, without self-limitation, in the different forms of organic degeneration, such as fatty heart, Addison's disease, chronic Bright's disease, diabetes mellitus, cirrhosis, and amyloid degeneration of the liver, etc. The same may be said also of the different forms of cerebral and spinal sclerosis, of pernicious anæmia, and of myxoedema.

Lastly, it is an exception to a very general rule of fatality when a case of trichinosis, with well-marked abdominal, muscular, and general symptoms, ends otherwise than in death within a few weeks.

Self-limitation is familiar in the natural history of typhus and typhoid fever, relapsing fever, yellow fever, cholera, diphtheria, whooping cough, mumps, small-pox, varicella, scarlet fever, and measles. In the sense of a definite duration of each paroxysm intermittent and remittent fevers are self-limited. Are they so also in tending toward recovery, without curative treatment within a certain time? This has been asserted, and in the case of remittent there is evidence that spontaneous cures do sometimes happen. Some observers aver that ague tends toward cessation of the chills after six, eight, or ten weeks. The obstinacy of the attacks in many instances under anti-periodic medication seems to make it probable that spontaneous recovery from intermittent hardly belongs to the typical natural history of the disease.

Whether the term self-limited can or cannot with propriety be applied to pneumonia and other acute inflammations, as pericarditis, etc., has been a mooted question. If it be so, it appears to the writer to be true in a different meaning of the word self-limitation from that in which it is applied to variola or typhoid fever. Yet some nosologists deny this distinction, and regard pneumonia as strictly a lung fever. Some of the facts supporting this view belong to the history of pneumonia as complicating malarial fever; e.g. in the winter fever of some parts of our Southern States. It must be admitted, however, that the inflammatory process, though morbid, is generally eliminative or corrective of a disturbing cause which produced it, and, unless that cause is continued or repeated in action, a limitation belongs to the succession of stages, ending either in resolution or in adhesions, serous accumulation, suppuration, or gangrene.

2. It is not necessary to dwell here upon the significance in prognosis of the patient's original constitution and hereditary or acquired predispositions, or on that of results left by previous attacks of illness. These are all obviously of importance. In a member of a family predisposed to consumption a bronchial attack following exposure may be much more dangerous than in others. So also a cause of mental agitation may produce insanity in a person who inherits a tendency thereto or who has before had an attack of mental derangement, while it would be innocuous to another who has no such proclivity. A second or third attack of delirium tremens is much more dangerous to life than a first attack. On the other hand, if yellow fever occurs at all in a patient who has before had it, the course of the disease is apt to be milder than usual. The most striking example of the influence of previous disease is seen in the comparative mildness of varioloid—i.e. small-pox modified by the system having been placed under the action of the vaccine virus.

3. Most important of all data in prognosis are, in most cases, the indications of the present state of the patient's system as to the performance of the organic functions, his sum of energy, and vital resistance and persistence. Especially must these indications be regarded comparatively; that is, ascertaining whether, in a period of weeks, days, or, sometimes hours (in malignant cholera even of minutes), the patient's general condition has been and is gaining or losing in the evidences of strength and healthy function of the great organs.

Every student of clinical medicine must become acquainted, as soon as possible, at the bedside, with these tokens and evidences, which make almost the alphabet of practice: What is a good, a doubtful, and a bad pulse? How does a patient breathe when moribund from simple exhaustion, and how does such respiration differ from the toil and struggle of asthma or the stertor of narcotism? Why does a glance suffice to make known to a surgeon the state of collapse after a railroad accident, or to a physician that of cholera or pernicious intermittent? What is the impression given to the finger upon the skin by intense fever, and what by the relaxation which precedes death? These and many other such questions are to be answered fully to each student only by the use of his own senses, with such interpretation as is to be obtained by the careful comparison of cases, with the aid of books and didactic instruction.

To a well-trained eye and hand a look and a touch will often suffice to make known the commencement of convalescence or of the precipitous decline toward death. Yet a wise physician will be very cautious in acting upon even seemingly obvious prognostications. Changes may be going on in important organs whose effects have hardly yet begun to show themselves, and which may after a while materially alter the aspect of the case. Particularly near the beginning of an attack of enthetic disease, such as scarlet fever, small-pox, typhus or typhoid fever, the physician should beware of too confidently forecasting the progress of the case for better or for worse. In nothing, probably, is the prudence of a practitioner more often or more severely tested than in his answers to inquiries made concerning prognosis.

4. Anticipation of the modifying action of remedies is undoubtedly a proper factor in our estimate of the probable result of any case of illness. Few diseases, however, are as yet so subject to control by specific medication as to allow certainty in such expectations. In a first attack of ague we may look with much confidence toward the speedy cure of our patient under quinia. In one who has had chills all winter even this confidence may need qualification. A sufferer with syphilitic rheumatism may generally be promised relief under the use of iodide of potassium, or one afflicted with scabies under the application of sulphur ointment. We seldom have misgivings about our ability to give relief in colic, constipation, or diarrhoea. Yet the first two of these may prove to be symptoms of intestinal obstruction resisting treatment, and the last may depend upon chronic ulceration of the bowel, giving it unexpected continuance. In all such instances careful and (when practicable) accurate diagnosis must precede prognosis; our estimate of the action of remedies becomes then a secondary, although often a valuable, part of the calculation of the probabilities of the case.

Prognosis in particular diseases involves the consideration not only of those signs of the general vital condition to which we have just been giving attention, but also of such as are more or less peculiar to each disorder. To a certain extent these signs may be grouped. We may refer to good and bad signs in pulmonary, cardiac, intestinal, renal, cerebral, and febrile affections respectively. Still, there will be for each malady, if it really has a distinctive character, some tokens which experience shows to be specially indicative of favorable or unfavorable progress and results.

Let us notice some of these as examples.

In pneumonia the best signs are the lowering of a high temperature, reduction of the number of respirations to 20 or 25 in the minute, expectoration of sputa less and less tinged with red or brown, and gradual reduction of the region of dulness on percussion. Worst, in the same disease, are an axillary temperature over 106°, respirations 40 or more per minute, with delirium, and expectoration becoming more abundant, grayish, and purulent; also with continued dulness on percussion and abundant mucous râles on auscultation.

In croup the best sign is, after a hoarse, dry, barking cough and dyspnoea, a soft, liquid râle, heard in the larynx and trachea during respiration or coughing. Worst, in croup, is a steadily or paroxysmally increasing difficulty of breathing, with a dry hissing or whistling sound of respiration and cough succeeding the barking sounds of the earlier stage.

In phthisis pulmonalis among the best signs are the patient's increasing in weight, coughing and expectorating less, ceasing to have hectic and night sweats. These may give renewed hope, even before much change is discernible in the physical signs. Of bad omen are intense hectic fever, incessant cough with abundant nummular sputa, copious perspirations, diarrhoea, breathing growing shorter and shorter, and extreme emaciation and debility.

In all organic affections of the heart an extremely rapid and irregular pulse, with orthopnoea and increasing anasarca, and especially the Cheyne-Stokes respiration (described under DIAGNOSIS), must cause unfavorable expectations.

In obstruction of the bowels the best of all symptoms is, usually, of course, a copious fecal evacuation. Yet a few cases have occurred in which a very large evacuation, delayed by obstruction for a week or two, has been almost immediately followed by collapse and death. The worst signs in cases of obstruction are (besides long-unyielding constipation) stercoraceous vomiting, a small, rapid pulse, and increasing coldness and clamminess of the surface of the body.

In cholera infantum the best signs are cessation of vomiting and purging, the discharges growing more nearly natural, the face becoming less shrunken in aspect, sleep taking the place of coma vigil or waking apathy, and water or milk, when taken, remaining on the stomach. Worst, in the same disease, are incessant rejection of everything swallowed, watery passages from the bowels every half hour or hour, shrinking of the face and body to skin and bone, with an apathetic expression of the open or half-open eyes, the latter rolling often from side to side.

In epidemic cholera good signs are the arrest of vomiting and of rice-water discharges from the bowels, rapid movement of the blood in the veins after removal of momentary pressure, return of natural color and warmth to the skin, with filling up of the pulse at the wrist. Bad signs in cholera are shrinking of the cheeks and of the flesh upon the hands, deepening ashiness or blueness of the skin, coldness and clamminess to the touch, dyspnoea, loss of pulse, incessant vomiting and purging of rice-water stools, constant cramps of the limbs, and suppression of urine.

In acute cerebral meningitis good signs are lessened temperature of the head, quiet sleep without stertor, disappearance of delirium, more natural pulse, and attention to surrounding objects, without disquietude. Bad signs in the same disease are deep stupor, strabismus, convulsions, paralysis, involuntary defecation and urination.

In typhus fever good signs are the pulse becoming slower and fuller, the skin less hot, more soft and moist, the tongue moist and clean, the face losing its dusky flush, and consciousness returning instead of muttering delirium.⁴⁰ Bad, in the same fever, are deepening of the flush of the countenance, profound stupor, rapid and feeble pulse, lying on the back and sinking down toward the foot of the bed, with suppression of urine.

⁴⁰ Incidentally, it may be mentioned that the return of the pulse to its normal rate is often considerably delayed in convalescence from typhus and typhoid fevers and other protracted diseases. If, then, the temperature is not above 99° F., and is stable from morning to night, the tongue is clean and moist, and appetite begins to appear, we need not be alarmed, although the pulse continues as high as 90 or 100 per minute, in a case attended by positive debility.

In typhoid fever many of the good and bad signs are the same as in typhus, belonging to closely similar general conditions. But in typhoid fever we observe also as favorable signs the lessening of tympanites, more nearly natural fecal stools, and the absence of tenderness in any part of the abdomen. As unfavorable, increase of tympanites and diarrhoea, sometimes large hemorrhages from the bowels; worst of all, at a late stage, sudden increase of abdominal distension, with dulness on percussion, coldness of the skin, great rapidity and feebleness of the pulse following perforation of the bowel, resulting usually in fatal peritonitis.

In scarlet fever, measles, and small-pox it is a favorable sign for the eruption to come out well at the usual time; its sudden recession threatens malignancy. In small-pox a confluent eruption marks a dangerous case, and so does the occurrence of distinct pustules in the throat. Early in scarlet fever stupor is very threatening, though not necessarily mortal. Late in the same disease bloody urine, or, worse yet, suppression of urine, may well cause alarm.

In all children's diseases the early occurrence of convulsions shows a severe but not always a dangerous attack. The late occurrence of convulsions is commonly much more serious in its significance.⁴¹ Convulsions are always of vastly less importance, prognostically, in children than in adolescents or adults. Yet they are always serious signs. While recovered from in the large majority of cases, they may at any time be fatal.

⁴¹ Yet I saw a case of acute cerebro-meningitis, in a girl ten years of age, in which a violent convulsion occurred on about the sixth day of the disease, and was followed by convalescence.

These enumerations, selected as examples merely, might be much farther extended but that the special prognosis of each disease will be fully set forth in the several articles upon them in the body of this work. Those now given may suffice for the illustration of the method and general principles by which the physician must be guided in his anticipation of the progress and result of cases of disease. The caution may be repeated, to observe great care in forming a conclusion in regard to prognosis in every instance, and still more in expressing it, unless in the presence of very clear and positive evidence.

HYGIENE.

BY JOHN S. BILLINGS, M.D.

The purpose of this paper is to indicate some of the ways in which hygiene, both private and public, is connected with the duties of the general practitioner, and to give some information as to modern methods of investigation and work in preventive medicine.

While the business of the physician is more especially the care of the sick with reference to the cure of disease, or, where that is beyond his power, as is too frequently the case, to relieve suffering and secure temporary ease for his patient, he is nevertheless often called upon to answer questions as to the causes of disease, and the best means of avoiding or destroying these causes. Not only does diagnosis often turn upon considerations of etiology, but a very considerable part of the treatment of actual disease must be hygienic in the broader sense of the word. The prescription or the surgical operation must not only be supplemented by advice as to residence, clothing, food, exercise, etc., but must, in many cases, be merely supplementary to such advice, which indicates the really essential method of treatment; and the giving this advice then becomes the most important part of the physician's work, although not usually recognized as such by his patients. The chief value of the prescription is, in fact, often to methodize the mode of life of the patient and to remind him at frequently recurring intervals of the regimen which has been ordered with it.

The physician has also certain duties in relation to the public at large, as well as to his individual patients, and these duties become more numerous and important as the density of population increases, so that in the large cities of most civilized countries he finds himself, nolens volens, in almost daily contact with legally constituted authorities in the shape of registrars, health officers, coroners, etc., and is not infrequently summoned before the courts as a supposed expert in matters connected with the public health.

Moreover, the physician who has become eminent in his profession is, in many cases the adviser, and, so far as professional subjects are concerned, to a great extent the guide, of those who legislate for, or execute the laws of, not only his own city or county, but his state and the nation; and he must to a corresponding degree be held responsible for the position which he takes and the advice which he gives in regard to public health matters. This is true whether his attitude on these subjects be active or passive, for his silence will be taken to mean that there is no necessity for action or change.

The limits of this paper do not permit the presentation of proofs and illustrations of these somewhat dogmatic assertions, but it is believed that they will meet with general assent from medical men without formal and detailed argument, and that it is unnecessary here to urge the interest or importance of practical hygiene upon the medical profession, or to enlarge upon the desirability that the practitioner, as well as the professional sanitarian, should be familiar with the conclusions of modern science and technology with regard to it.

In the minds of many intelligent and thoughtful physicians there is, no doubt, a feeling of unformulated distrust as to the real possibilities or probabilities of improving the health and diminishing the mortality of the community at large; and this feeling is in part due to the exaggerated claims and emotional exhortations of some advocates of hygiene. A careful and unprejudiced survey of what has been accomplished by sanitary measures will, however, largely dissipate this distrust.

The natural term of the life of man is fixed by the physiologist at about one hundred years, which is nearly in accordance with the law indicated by Flourens, that the period of life of an animal is about five times that required to perfect the development of its skeleton and unite the epiphyses with the shafts of the long bones. The actual average duration of human life is less than half this, but there is satisfactory evidence that it has increased in civilized countries. The ancient estimate is expressed in David's declaration, that "the days of a man are threescore years and ten, and if by reason of strength they be fourscore years, yet is their strength labor and sorrow." Kolb, a cautious and learned statistician, concluded, from his studies, that while the maximum age reached by man has not materially changed for many centuries, the number of persons who now survive infancy and of those who reach a ripe old age has decidedly increased; and this opinion is sustained by Mr. Lewis, the secretary of the Chamber of Life Insurance of New York, who points out that while civilization largely interferes with the laws of evolution by survivorship, it aids by economizing the waste which occurs in its absence. "Under natural selection, when variations in capacity arise, thousands of them are wasted where one is secured, fixed, and transmitted. But human society economizes much of this waste, fastens upon and improves an immensely larger proportion of the capacities lavishly produced by Nature, and thus concentrates forces which would otherwise spread their operation over countless ages."¹

¹ "Influence of Civilization on the Duration of Life," Reports Am. Pub. Health Ass'n, N.Y., 1877, vol. iii. p. 173.

We have, however, no record of the duration of life in ancient Greece and Rome, and it is quite possible that it was greater than in Western Europe during the Middle Ages, which formed a period of retrogression in a sanitary point of view. The Jew, the Greek, and the Roman, prior to the Christian era, were probably cleaner in person and in dwellings than the people of the time when dirt became the odor of sanctity.

In the absence of reliable data for this country, it is impossible to speak with certainty of the results of attempts made here to prevent disease and death. Each sex, race, and age has its own rate of mortality, and until this rate is determined we can only guess as to whether good work is being done or not.

We can never hope to diminish the total number of deaths which will occur in long periods, say two hundred years, but we may rationally try to prolong the average duration of life, to diminish infant mortality, and to secure greater comfort and better health for individuals and for the community at large.

The reader must remember that only a mere outline of the subject can be presented here; the details would require several volumes, and the tendency to specialization in this, as in other branches, is so great that it is hardly to be expected that any one man shall have either the theoretical or the practical knowledge necessary for covering the entire field. There are certain things in relation to hygiene which every physician should know; there are many other things with regard to which it is sufficient if he knows where to find full and reliable information when he needs it. With this preface we will pass at once to our subject, which may be conveniently divided as follows:

I. Causes of disease, means of discovery, and prevention.

II. Personal hygiene in its relations to the practice of medicine.

III. Public hygiene in its relations to physicians.

I. Causes of Disease, Means of Discovery, and Prevention.

Although the origin of disease has from the earliest times been the subject of study by medical men, the physician has not heretofore, usually, been called upon to investigate the causes of disease in particular localities, until the occurrence of sickness in that locality has called attention to the matter. The education of the public as to the importance of sanitary work has, however, recently made great progress, and it is now not unusual to ask the opinion of the family physician as to the healthfulness of a given locality or house. The question may be presented in three different ways: First. In a given case of disease, what is the probable cause? Second. Given the presence of a known or suspected cause of disease, what are the best means of avoiding or destroying it? Third. In the absence of cases of disease, to determine whether causes of disease are probably present, and if so, what causes.

The word "cause" is here used in its widest sense, including not only what are commonly called predisposing and exciting causes, but also those conditions which aggravate or continue the disease. These causes may be roughly classed as follows: Heredity; impure air; impure water; climate; habitations; occupation; food; intemperance of various kinds; clothing; errors in exercise; sexual errors; parasites; contagia; expectant attention and other mental causes, including worry, etc. In most cases two or more of these classes of causes are combined in action for the production of a given case or outbreak of disease, and when we refer any disease to a single factor, what is meant usually is, not that this is the sole and exclusive cause, but that it is the most prominent one.

Bearing this in mind, let us consider briefly some of the causes above mentioned.

I. HEREDITY.—That the child inherits from its parents its physical type, including color, stature, physiognomy, temperament, and certain peculiarities of structure or arrangement of internal organs, is well known. This hereditary influence is stronger from the immediate than from the remote ancestry, although the curious phenomena of atavism sometimes form exceptions to this rule. The hereditary causes of disease can be guarded against when known. Theoretically, by preventing generation on the part of persons who are unfit to produce offspring; practically, to a certain extent, by taking special precautions against these causes and their effects in the individual, particularly at those ages in which these influences seem to have their greatest force. The most important of these hereditary diseases are syphilis, consumption, scrofula, cancer, gout, certain skin diseases, insanity, and criminal tendencies of various kinds.

The physician's advice is rarely asked with regard to the propriety, from a sanitary point of view, of a proposed marriage, nor is it often taken when given, unless, indeed, it happens to correspond with the wishes of the recipient; nevertheless, he is occasionally in a position to exert influence in such a matter, and when this is the case the following general rules may be borne in mind: 1. No marriage should occur between persons having the same hereditary tendency to disease; and this is especially important in marriages between relatives. 2. A girl should not marry under the age of twenty. 3. A person affected with hereditary or well-marked constitutional syphilis, or having a strong consumptive taint, or tendency to mental unsoundness, should not marry at all.

The precautions to be taken in individual cases in which there is a known hereditary predisposition to certain diseases will probably be indicated in the articles upon those special diseases. The most important of these, from the sanitary point of view, are consumption and gout, partly because of their frequency, partly because of the undoubted power which a proper regimen, applied in time, has in controlling them. The pain in gout has often an excellent sanitary effect; it is an inducement to temperance much stronger than any amount of good advice.

The influence of heredity in producing abnormities of refraction and accommodation of the eye, and the importance of detecting these early and giving them proper treatment, have not hitherto received, from the general practitioner, the attention which they deserve. Children of parents affected with astigmatism, ametropia, etc. should be carefully examined before being placed at school, and if necessary fitted with proper glasses.

The heredity of idiosyncrasies as to certain articles of food or certain drugs must also be borne in mind by the physician, for, although implicit confidence is not always to be placed in the statement of a patient that he cannot take a certain medicine, yet a knowledge of the facts will occasionally save the prescriber from some awkward mistakes.

The importance of bearing in mind the family peculiarities is best appreciated by the old family doctor who has had two or three generations pass under his hands: he knows, for example, that in one family he may expect brain complications, in another lung troubles, and that what would be grave symptoms in one house are of comparatively small import in another. Unfortunately, the greater part of this kind of knowledge has not yet been formulated, and each physician has to acquire it for himself; but he will find the process of acquisition greatly facilitated if in all cases in a new family he makes it a rule to learn something of the medical history of the parents, and he will find intelligent laymen quick to appreciate his inquiries in this direction.

The importance of taking into account hereditary influences is well illustrated by the care which is taken to obtain information with regard to them in well-conducted life insurance companies. The medical examiners of such companies have their attention specially called to this matter, and the following extract from a manual of instructions shows how it is regarded from a business point of view: "If consumption is found to have occurred in the family of the applicant, he is to be regarded not insurable under the following circumstances, viz.:

YEARS OF AGE.

If in both parents, not insurable until 40

If in one parent, not insurable until (Except for ten-year endowments, then 20 years.) 30

If in two members (not parents) 35

If in one member (brother or sister) (Except for ten-year endowments, when peculiarly favorable.)" 20

If apoplexy, paralysis, or heart disease is found to have occurred in any two members of the applicant's family, he is to be regarded as insurable only upon the endowment plan, the term of insurance to expire prior to his reaching the age of fifty years. If insanity shall have so occurred (in two members), a provisionary clause is essential, and is attached to the policy by the company.

II. IMPURE AIR.—The dangers of impure air, water, and food depend largely upon the fact that through these media may be introduced into the body particles of organic matter, living or dead, which tend to produce disease in the recipient. The parasites are types of this mode of disease-production, and these blend with the contagia of the specific diseases in such a way that it is not easy to draw the distinction in all cases. There are also certain poisonous gases and inorganic compounds which may occasionally be present in air or water to such an extent as to produce disease; but as a rule the gaseous impurities of the air are offensive to the smell rather than dangerous, as will be seen when we come to consider the effluvium nuisances.

The subject of ventilation, for the purpose of procuring an adequate supply of pure air, is one of so much importance, and one upon which the physician is so liable to be called for practical advice, that it seems proper to state briefly the general principles which should govern investigations into, or recommendations upon, this subject.

The impurities of air which are to be disposed of by ventilation are for the most part derived from the human body, chiefly from respiration, and these only will be considered here. In some cases it is necessary to make special provision for the products of combustion from gas, etc., but as a rule this is rather for the purpose of regulation of temperature than anything else. The impurities of air due to the presence of human beings consist mainly of carbonic acid, ammonia, sulphuretted hydrogen, and sulphide of ammonium, and of various organic compounds, mostly in the form of minute particles of organic matter of uncertain structure, but extremely prone to decomposition. It is usual to estimate the degree of impurity by the amount of carbonic acid present, and this leads many persons to suppose that the carbonic acid is in itself the chief and most dangerous impurity. This gas is, however, not perceptible to the senses, nor is it injurious to health, unless present in much greater proportion than that in which it will be found in the most crowded habitations or assembly-rooms. Its importance in questions of ventilation depends upon the fact that its increase in a room beyond the amount present in the outer air may usually be taken to be in direct proportion to the amount of the really dangerous and offensive impurities present, and that the amount of carbonic acid can be ascertained by chemical tests with comparative ease and rapidity; which is not the case with regard to the organic matter. The carbonic acid is therefore taken as the measure of the impurity, although it is not itself the impurity of which we are most anxious to be free.

To decide as to whether a room is well ventilated or not, some standard of permissible impurity must be fixed, and this standard is now usually taken to be, in a room occupied by human beings, that condition of air which produces in a person having a normal sense of smell, and who enters from the fresh air, a faint sensation of an odor very slightly musty and unpleasant. Upon testing the air of such a room, it will be found that the amount of carbonic acid impurity present—that is, the excess of this acid over the amount in the external air—will be between 2 and 3 parts in 10,000.

As the amount of carbonic acid in normal air varies from 2 to 5 parts in 10,000 in different places, and in the same place at different times, it is better to look to the carbonic acid impurity as above defined rather than to the total amount of the acid found present, if strict accuracy is desired; but usually the statement of Dr. Parkes is correct, that the organic impurity of the air is not perceptible to the senses until the total carbonic acid rises to the proportion of 6 parts in 10,000 volumes. When the carbonic acid reaches 9 parts in 10,000 the air is close, and when it exceeds 1 part in 1000 the air is usually decidedly unpleasant. If we take 2 parts in 10,000 as the permissible maximum of carbonic acid impurity, it follows that the amount of fresh air which must be supplied and thoroughly distributed for each person per hour is 3000 cubic feet. If 3 parts per 10,000 be taken as the permissible maximum (which is the standard of Pettenkofer), the amount of air per head per hour must be 2000 cubic feet. While it is impossible, as Dr. Parkes remarks, to show by direct evidence that the impurity indicated by 7, 8, or even 10, parts of carbonic acid per 10,000 is injurious to health, it is advisable to accept his standard, because it is a simple one, and can be practically applied without special apparatus or technical skill, and because there is evidence of the injury to health which continued exposure to air impure, by this standard, ultimately produces.

Keeping this standard in view, the physician may be called on for an opinion as to whether the ventilation of a given building is satisfactory or as to the merits of a proposed plan for ventilation. The first is a question of fact: What are the effects produced upon the inmates? Are there unpleasant odors in the building or not? What percentage of carbonic impurity is present? What is the number of cubic feet of air per head that is introduced and removed per hour? And what is the character of the fresh-air supply as to purity? Does it come from the cellar, or from other rooms, or from a foul area? Air-currents can usually be best investigated by the fumes of nascent muriate of ammonia produced by exposing a cylinder of common blotting-paper, moistened with dilute hydrochloric acid, to the vapors coming from a crumpled fragment of the same paper moistened with common aqua ammonia and placed within the cylinder. The process for carbonic acid determination is simple, and can be learned in three hours in a laboratory under a skilful teacher. It does not seem worth while to describe it here. The determination of the amount of air passing through a given register, flue, or chimney in a given time is to be made by the use of an anemometer, an instrument which registers the velocity of the current of air passing through it.

In judging of the merits of a plan of ventilation the following points should be remembered: The defect in most plans for ventilation is in the air-supply. Many people suppose that they have made all necessary provision for ventilation if they have put in tubes or openings for the escape of foul air, forgetting that these outlets will have no effect if corresponding inlets are not provided. Examine, first of all, therefore, the ducts, flues, and openings proposed for the fresh-air supply, with reference to their size and position and the amount of air to be furnished by them. These will almost invariably be found to be too small. The proper size of flues and registers for a given room is ascertained by dividing the number of cubic feet of air to be supplied per second by the velocity in feet per second which the air is to have in the flue or opening, bearing in mind that it is much better that these flues and registers shall be too large than too small, since it is easy to reduce their capacity, but, in most cases, impossible to increase it. When the fresh-air register is so situated that the current of air from it is liable to strike upon the person of an occupant of the room, the velocity of this current should not exceed 1½ feet per second if unpleasant draughts are to be avoided; and it will usually be found best that the velocity of the air in the flue shall not exceed 6 feet per second, except in the case of very large flues, where the element of friction becomes of comparatively small importance. In the great majority of cases the amount of air to be supplied depends upon the number of persons, and not on the cubic space; but in exceptional instances, where the amount of cubic space is very large in proportion to the number of persons, and the heating is effected by warm air, it may require more air to keep the room at a comfortable temperature than is necessary for the supply of the occupants. The cubic space is also relatively much more important in rooms which are to be occupied but a short time continuously, and can then be thoroughly aired, than it is in rooms constantly occupied.

The methods of calculation can be best illustrated by one or two examples. What should be the number and size of flues and registers for fresh-air supply for a hospital ward to contain 24 beds, the ward being a rectangular pavilion with windows on opposite sides? In this case the room is constantly occupied, and the supply of air should be 1 cubic foot per head per second, or, in all, 24 cubic feet per second. The velocity of current at the registers should not exceed 3 feet per second—better only 2. This will require from 8 to 12 square feet of clear opening in the registers. If we allow four on each side of the room, each register must have at least 1 square foot of clear opening. The velocity of the air in the flues supplying these registers should not exceed 4 feet per second, and therefore the area of each flue should be about 9 by 12 inches. Suppose the same question be asked with regard to a school-room to contain 48 pupils. In this case the room will not be occupied more than two hours at a time. The air-supply desirable may be put down at 35 cubic feet per head per minute, or 28 cubic feet per second for the whole. The velocity in the flues may be put, as before, at 4 feet per second; hence we need 7 square feet area of flue, or seven flues, each having 1 square foot of area. It is safe to say that there are not twenty school-houses in the United States which have fresh-air flues of sufficient area; the deficiency is made up, for the most part, by leakage of the outer air through cracks around windows and directly through the wall, and also by the passage of air from the central hall into the room, this last air coming from the cellar or basement.

The velocity of the air at the foul-air registers and in the foul-air ducts may be greater than in the fresh-air flues, since there is no danger of its causing draughts, and hence there is no truth in the common notion that the outlets should be larger than the inlets to allow for the expansion of heated air. It is important that the velocity of the current in the outlet shaft or chimney should be at least 8 feet per second at the point where it escapes into the outer air; and if the outlets be too large for the inlets, the result may be that some of the foul-air flues will work backward and become inlets. The plan of making everything a little larger than is necessary is not a safe one as regards chimney-flues and outlet shafts.

The merits of a plan of ventilation depend not only on the amount of air introduced, but on its distribution. The test for distribution is chemical analysis of samples taken in different parts of the room and at different levels. A very good idea of the direction taken by the incoming air can also be obtained by the use of fumes of nascent muriate of ammonia, as above described. In considering the distribution which will probably take place in a given plan, care should be taken not to fall into the common error of supposing that because pure carbonic acid gas is heavier than air, therefore the carbonic acid derived from respiration sinks to the floor, and that special provision should be made to remove it at that point. The law of the diffusion of gases effectually prevents this separation and sinking of the carbonic acid from the mixture of gases expired, and it will be found to be present in about equal proportions in all parts of an inhabited room.

The methods of introducing and distributing fresh air depend to a great extent upon the methods of heating employed; and it is necessary to remember that while good ventilation is a very desirable thing, satisfactory heating is, in cold weather, still more desirable, and must be attained even if the ventilation is interfered with for that purpose. The principal difficulty in the way of securing good ventilation is its cost. In a cold climate satisfactory heating, good ventilation, and cheapness are not compatible; it is comparatively easy to obtain any two of them, but impossible to have the three together. This fact should be fully understood and realized by the physician, for its comprehension will save much time in considering the merits of various patent ventilators and ventilating appliances, which, according to their inventors, produce good ventilation at no expense beyond that of the original cost of the apparatus; which is practically about the same as a claim to have discovered perpetual motion. Patent ventilators are usually cowls to be placed upon the top of outlet flues. I know of none which are superior to the common Emerson Ventilator, on which there is now no patent. In cold weather the air must be warmed to secure comfort; it must be changed to secure ventilation. The changing of the air carries off heat, the loss of which must be supplied by fuel, which fuel costs money. The greater the ventilation, the more rapid the change and the more heat required. It is therefore quite possible to judge somewhat of the merits of a heating and ventilating apparatus—for example, of a school-house—from the amount of fuel consumed; but the conclusion will be precisely the reverse of that drawn by the average trustee, since it will be, that within certain limits the less fuel required the less satisfactory the apparatus.

The evil effects of insufficient ventilation, although very certain and very serious, are not immediate, or such as to attract attention at first, except in very aggravated cases with excessive over-crowding. The power of the organism to adjust itself to surrounding circumstances is very great, and perhaps as great in regard to the endurance of foul air as anything else. Yet this power is greater in seeming than in reality, for at last such air produces disease and shortens life. Its effects are manifested in diseases of the respiratory organs, acute and chronic, and it is now generally admitted that the undue prevalence of phthisis in troops is due to the foul air of the barrack-rooms.

Some persons are much more susceptible than others to the effects of impure air, and will suffer from headache, languor, loss of appetite, etc. where others would experience little inconvenience. Children thus susceptible dread the school-room as ordinarily constructed and ventilated, and their discomfort should be taken into account and guarded against.

Thus far, reference has been made only to those impurities of air due to respiration and lights; in other words, the necessary impurities found in human habitations. The impurities due to sewer gases will be referred to hereafter; they should be prevented absolutely, and not provided for by ventilation. One of the most difficult problems presented to the physician is to determine whether the effluvia from a given locality are injurious to health, and if so, to what extent. These effluvia may be due to certain occupations or manufactures, or they may result from the disposal of excreta, from obstructed drainage giving rise to swamps and the collection of decaying organic matter, and in other ways. The best definition of the term "injurious to health" in this connection is perhaps that suggested by Dr. Ballard—i.e. that exposure to the offensive effluvia causes bodily discomfort or other functional disturbance, continuing or recurring as the exposure continues or recurs, and tending by continuance or repetition to create an appreciable impairment of general health and strength, to render those exposed more liable than others to attacks of disease, and more apt to suffer severely when attacked, and, in the more serious forms, to the direct production of the disease and the shortening of life.

The group of symptoms due to offensive effluvia is, as Dr. Ballard remarks, a tolerably constant one, and consists of loss of appetite, nausea, headache, giddiness, faintness, and a general sense of depression, with, in some cases, vomiting and diarrhoea. But it is usually impossible to prove by statistics that these phenomena are due to a given effluvium complained of, for those who suffer from it are usually exposed to other causes of ill-health, such as poverty, overcrowding, collection of filth, etc.; and, on the other hand, many of those exposed to the effluvium seem to suffer very little, if at all, from their surroundings. And so true is this, that in the carefully prepared report upon effluvium nuisances recently issued by Dr. Ballard,² it will be found that as a rule no attempt is made to prove that the effluvia from any particular branch of industry are injurious to health; the test practically applied is that they produce offensive odors.

² Report in respect of the Inquiry as to Effluvium Nuisances arising in connection with various Manufacturing and other branches of Industry. By Dr. Ballard, London. Her Majesty's Stationery Office, 1882, 8vo.

The legal view of this subject is given in the various decisions as to what should be considered a nuisance, the essence of which is the use of one's own property in such a way as to inflict damage upon, and injure the rights of, another. If a man collects on his own premises, for his own use, any material, such as water or filth, he is bound to retain it within his own premises or to let none of it escape in such a way as to damage others; and this holds good as regards gases, vapors, and odors. The decision of Mansfield, in the case of Rex vs. White, is often quoted approvingly by jurists, viz.: "It is not necessary that the smell be unwholesome; it is enough if it renders the enjoyment of life uncomfortable." But, practically, the question as to whether the discomfort produced is sufficient to produce ill-health will be the one upon which the physician is called to give evidence, and the one also upon which he will find it most difficult to obtain data sufficient to enable him to form a positive opinion.

III. IMPURE WATER.—Of all the various preventable or removable causes of disease to which the attention of the physician engaged in practice in the small towns and rural districts is directed, it will usually be found that the water-supply is the most important, because it is in these localities that it is most liable to become contaminated in such a way as to produce sickness.

All water used for drinking purposes is impure in the chemical sense, since it contains some inorganic matters or salts, and in most cases organic matter also. It is difficult to define precisely what should be considered an impure water in a sanitary sense, and the best we can do is to indicate probabilities in the absence of positive evidence of the production of disease by the suspected water. So far as inorganic impurities are concerned, the most important, from the sanitary point of view, are the salts of lead, magnesia, and lime, but in this country these are so rarely the cause of disease that they hardly require special notice. The physician should, however, bear in mind possibilities of lead-poisoning in some obscure cases which he will meet.

The diseases due to impure water are certain specific fevers, diarrhoeal diseases, and some affections due to parasites which find entrance to the body through this medium. The water-supply is to be suspected in case of prevalence of diarrhoeal disease in a community, and especially if the outbreak be sudden and affect a number of persons and families. Sudden outbreaks of cholera, typhoid fever, or malarial fever, confined to a limited locality, should lead to careful examination of the water-supply. The impurity in water which causes these diseases is supposed to be either organic or the product of organic life, and at present the prevailing opinion is that the really dangerous impurities consist of minute living organisms or germs. It is usual to estimate the impurity of water by the amount of organic matter present, but it is evident that this alone can give no positive information, since by this standard milk and soup would be very dangerous. Much depends upon the character of the organic matter, whether it is derived from the animal or vegetable kingdom—whether it is in a state of fermentation or putrefaction, etc. etc.; but the presence of specific germs in it is the most important part of all, and at the same time the most difficult to ascertain. Nitrogenous organic matter in a state of decomposition is dangerous, yet it does not always produce disease, even when ingested in comparatively large quantity, as in case of "high" game or tainted meat; and it is easy to find instances where water strongly polluted with sewage has been used for a considerable period without producing marked ill effects. It is, however, so extremely probable as to be for practical purposes certain, that water contaminated with the discharges from persons suffering from certain diseases will produce similar diseases in those who drink it, and there is also enough evidence that water containing filth of various kinds either produces or promotes disease to warrant much more attention to this subject than has heretofore been bestowed upon it.

The chemical examination of a suspected water is by no means a simple process, and in most cases had better be referred to an expert in such matters. It is highly desirable, however, that the physician should have sufficient technical knowledge to be able to make a rough analysis at least, if for no other reason than that he may be able to appreciate the results reported by the chemist. As a rule, when a water is so polluted with decomposing organic matter as to be positively dangerous it will have an unpleasant odor, which is best developed by half filling a quart bottle with the water to be examined and shaking it thoroughly. The so-called simple and ready methods which are from time to time advocated in the newspapers, such as the addition of sugar to the suspected water and allowing fermentation to take place, the use of tannin as a precipitant, or the decolorization of a solution of potassium permanganate, are really of very little value and should not be relied upon. In the hands of an expert the best simple method of determining the quality of a water is by evaporation of a known quantity and the ignition of the solid residue. From the amount of the total residue, the quantity left after ignition, the amount of blackening produced, and the odor, a very fair opinion can be formed as to the amount of organic matter present, and whether it is of animal or vegetable origin.

It is not within the province of this paper to describe the methods used by chemists in water analysis, of which the principal are known as the Franklin and Armstrong, the Wanklyn, and the permanganate methods. A careful examination of these methods has recently been made under the direction of the National Board of Health, and a preliminary note of the results, prepared by Professor Mallet, has been published in the Bulletin. From this it appears that the chief value of chemical analysis is, first, the verification of gross pollution, which will usually be detected by the appearance and smell of the water; and, second, in periodical examination of a water-supply to detect changes from the normal or usual character of the water, which may be taken to have a certain local standard of purity. Special importance is attached to the careful determination of nitrates and nitrites in water to be used for drinking, these being the results of oxidation of organic matters, and therefore giving evidence of previous contamination.

Prof. Mallet concludes that "there are no sound grounds on which to establish such general standards of purity as have been proposed, looking to exact amounts of organic carbon or nitrogen, albuminoid ammonia, oxygen of permanganate consumed, etc., as permissible or not. Distinctions drawn by the application of such standards are arbitrary and may be misleading." While this is perfectly true, considered from the standpoint of scientific precision, it does not sufficiently take into account the value of probabilities in these matters, considered as motives to action. It is perfectly true that there can be no fixed standard—that a water which the chemist would report as relatively pure might be much more apt to produce disease than one which he would pronounce impure—but it is nevertheless true that from the results of chemical analysis, taken in connection with evidence as to the source and history of the water, an opinion can be formed as to the danger from its use which is sufficiently reliable to be acted upon in the absence of positive evidence, such as the production of disease.

In many cases the matter must be doubtful, and Prof. Mallet truly says that it will not do in all such cases to forbid the use of the water, for it often happens that this should not be done unless it is absolutely necessary; but there are many other cases in which there is very little doubt, and where action should be governed by the probabilities.

The microscopical examination of suspected waters sometimes gives decided indication as to the nature of the impurities; and it may be that hereafter, in connection with physiological tests, it will become of even more importance than the chemical. To determine the presence of organisms in a sample of water the best method known at present is to kill and coagulate them by means of osmic acid or chloride of platinum, and allow them to subside. This method is of course inapplicable if it be desired to use them for either culture- or inoculation-tests.

Chemists have no uniform system of reporting the results of their analyses, some using grains per gallon, U.S. or Imperial as may be, and others parts per hundred thousand or per million of the water. It is therefore difficult to appreciate the value of the figures as given by them. The following, in parts per 100,000, will enable the practitioner to form a general estimate of the character of analytical reports; but the opinion in individual cases is so modified by the coincident amounts of chlorine, ammonia, nitrous and nitric acids, that the experienced sanitarian only is qualified to put on the results an estimate which shall be in accordance with our present knowledge of such matter:

Upland Surface-Waters.

Allowable. Doubtful. Impure.

Total organic elements to .4 .4 to .6 Over .6

Oxygen required to .3 .3 to .4 Over .4

Albuminoid ammonia to .015 .015 to .025 Over .025

All Other Waters.

Total organic elements to .2 .2 to .4 Over .4

Oxygen required to .15 .15 to .2 Over .2

Albuminoid ammonia to .010 .010 to .015 Over .015

In connection with impure water should be mentioned impure ice. Ice is purer than the water from which it forms, but if cut on a foul pond it will itself be foul, and the vitality of some microscopic organisms is not destroyed by their being frozen, as is shown by the fact that samples from the centre of blocks of ice will inoculate sterilized infusions with the germs of putrefaction, precisely as the water of which the ice is composed would have done before it was frozen. Disease has been traced to impure ice, and it may be that it is more frequently due to this cause than has heretofore been supposed; at all events, it is well to bear the possibility in mind.

The subject of impure water will be further considered in speaking of habitations.

IV. CLIMATE.—The literature of the effects of different climates upon the human body is very extensive, following the general rule that the less positive or precise knowledge there is upon a given subject the more will be written about it. Of all animals, man seems to adapt himself most readily to the extremes of climate; and, although it is commonly supposed that a tropical climate is injurious to those coming from cooler regions, yet it has been found that where he takes the same precautions to ensure cleanliness, pure water and air, and proper food, the European does not have a higher rate of mortality in Algeria or in the East or West Indies than he does at home, if the effects of cholera and yellow fever be excepted.

Dr. Parkes defines the effect of climate upon the human body to be "the sum of the influences which are connected with the solar agencies, the soil, the air, or the water of a place;" in other words, he makes it nearly equivalent to the locality or the environment. By "climate" we understand, commonly, the sum of meteorological influences, the most important of which, as regards health, are temperature, humidity, and wind. The effects of temperature in producing disease are often confounded with the effects of change of temperature, which last is perhaps the more important of the two, and should be specially borne in mind in advising climato-therapy for chronic or wasting diseases.