committed great ravages, particularly in the Middle Ages, and an epidemic of the fourteenth century is especially notorious, which has been designated the "black death" because hemorrhage from the lungs occurred with extreme frequency. Occasionally onefourth of the population has succumbed to the plague. Only since the middle of the nineteenth century has the plague disap

peared from Europe, although there is yet always danger of renewed importation from Asia, where, particularly in recent years, extensive epidemics of the disease have again occurred.

The exciting agent of plague is believed to be the plague-bacillus (Fig. 66) discovered by Yersin and Kitasato in 1894-a rod with rounded extremities, which stain more deeply with methylene-blue than the middle. Not only has it been possible

to grow plague-bacilli in pure culture, and to inoculate animals successfully with them, but involuntary inoculation of human beings with cultures of plague-bacilli has recently occurred in one of the clinical laboratories at Vienna, as a result of which three persons succumbed. Plague-bacilli are found in the purulent accumulations of the disease, in inflamed lymphatic glands, in the enlarged spleen, occasionally in the blood, and it is said also in large number in the urine and the feces, and, in cases of plague-pneumonia, also in the expectoration.

Plague-bacilli not rarely gain entrance into the human body through small cutaneous wounds, particularly fissured wounds of the hands and feet being especially dangerous in this connection. At times the tonsils constitute the portal of entry for plaguebacilli. Occasionally plague-bacilli are inhaled, and thus give rise to plague. It is still a debatable question whether infection may take place through the stomach and intestines from plaguebacilli that have been swallowed. Infection may take place through immediate contact with plague-patients, through inanimate objects, through the air, or through the intermediation of a third person. The dirtier and the more careless the mode of life in a community, the more readily does plague spread. For this reason the disease does not become extinct in the Orient. Rats appear to play an important role in the dissemination of the pestilence, as they are attacked in large numbers during the prevalence of an epidemic of the plague, and their number is almost unlimited

in the Orient. Some insects, also, may convey the infection, as it has been possible to demonstrate the presence of plague-bacilli in the blood of fleas that have been removed from rats suffering from plague.

Symptoms.-The period of incubation of plague varies from two to seven days. In accordance with the clinical manifestations three varieties of plague have recently been distinguished, and these have been designated bubonic, septic, and pneumonic plague.

Bubonic plague generally begins with a chill, which is followed by elevation of temperature to 39° or 40° C. (102.2° or 104° F.) and above. Soon the peripheral lymphatic glands become the seat of pain and swelling; thus, the inguinal, brachial, axillary, submaxillary, cervical lymphatic glands. The enlargement of the lymphatic glands is frequently by no means symmetric, and some collections of glands are conspicuous on account of the especially advanced inflammatory alterations they present. Some packets of glands begin to exhibit fluctuation in the course of two or three days, and finally rupture externally. In many patients this is followed by material improvement in the general condition. The spleen is almost always enlarged. The general condition may be affected in various ways. Some patients feel scarcely ill, and are unwilling to remain in bed, while others are vertiginous, become comatose, and occasionally die within the shortest possible time from exhaustion and cardiac paralysis.

In cases of septic plague either the enlargement of the lymphatic glands pursues the course described, or the alterations in the glands are confined to slight swelling and tenderness. The patients exhibit profound collapse, and, above all, hemorrhages take place from the stomach and the intestines. The disease generally pursues an unfavorable course if plague-bacilli can be demonstrated in the blood.

Plague-pneumonia resembles ordinary pneumonia, although, in addition to pneumonia cocci and streptococci, plague-bacilli also are present in the expectoration.

The duration of an attack of plague is from one to two weeks. Among the complications parenchymatous keratitis especially is to be mentioned, not rarely terminating in suppuration and destruction of the eye.

Diagnosis. Since the discovery of the plague-bacillus the diagnosis of the plague has been possible with certainty. Isolated instances were formerly confounded with especial frequency with syphilis. Plague-bacilli can but rarely be found directly in the blood. It is well to prepare an agar-culture from the blood, in which the plague-bacilli will develop in the thermostat within fortyeight hours, and can be distinguished by their bluish-gray color.

Prognosis. The prognosis of plague is serious, as in not a few epidemics the mortality has been as high as 90 per cent.

Anatomic Alterations.-Post-mortem examinations show that not only the external, but also the internal, lymphatic glands are involved in inflammatory swelling. The spleen and the intestinal follicles also are enlarged and swollen. On microscopic examination necrotic foci are found in the organs named. In cases of septic plague purulent accumulations are present in various organs, and, in cases of plague-pneumonia, bronchopneumonic or lobar areas of inflammation.

Treatment.-Blood-serum therapy has been recommended as a specific in the treatment of plague, although its success has been questioned from various sources. Accordingly, expectant treatment, or, in the presence of threatening symptoms, symptomatic treatment, must be resorted to. The latter includes the use of stimulants. It is doubtful if inunctions with mercurial ointment exert any influence upon the enlarged lymphatic glands. Suppurating lymphatic glands should be incised with the knife and be disinfected. Haff kine has recommended protective inoculations as a prophylactic measure. The future must decide whether these are of practical value. For the present, it is more important to isolate patients suffering from plague, to burn their possessions, or to disinfect them with great care, and also to sterilize the urine, the feces, the expectoration, and the pus. It is important to exercise most scrupulous domestic and personal cleanliness and to insure the destruction of rats.

IV. INFECTIOUS DISEASES ATTENDED WITH LOCAL ALTERATIONS IN THE RESPIRATORY ORGANS.

WHOOPING-COUGH (PERTUSSIS).

Etiology.-Whooping-cough is preeminently an infectious disease of childhood; only exceptionally does it occur in adults also. In the latter event it attacks principally women, especially pallid, irritable, and nervous women. Pregnancy also appears to constitute an influence predisposing to infection. Further, females seem to predominate among the victims of the disease even in childhood, and this has been attributed to their more readily irritable nervous system.

The infective agent of whooping-cough is as yet unknown, and the bacteria and protozoa that have hitherto been found in the sputum of patients lack confirmation. Clinical experience shows that infection may take place through contact, through the air, through the intermediation of a third person and of inanimate objects. Most children acquire the infection in walking out of

doors, on playgrounds, or in school. The infective material is correctly suspected to be contained in the sputum. As it is customary to advise patients with whooping-cough to spend a good deal of time walking in the open air, and as many patients eject their sputum indiscriminately upon the street, where it readily dries and is converted into dust and is inhaled by healthy individuals, it will be readily understood that whooping-cough, by reason of its often long duration, is peculiarly capable of giving rise to a large number of sources of infection. Most children are attacked between the first and the seventh year of life. Within the first six months of life infants generally remain exempt, possibly because they are little exposed to the air, and then often wear veils. Whooping-cough has, however, been observed at times to occur in the first days of life if the mother had suffered from the disease during pregnancy. Those who have passed through an attack of whooping-cough generally remain exempt from subsequent infection, as a result of acquired immunity.

Whooping cough may occur sporadically, endemically, and pandemically, and not rarely children who leave their homes with whooping-cough in order to avail themselves of the favorable influence of change of air constitute the source of an epidemic in healthy places. In large cities epidemics of whooping-cough not rarely recur at fairly regular intervals, which generally vary from two to four years. Not rarely epidemics of whooping-cough immediately precede epidemics of measles, scarlet fever, Rötheln, or chicken-pox, or they may exist simultaneously, or the former may follow the latter. It may also happen that a child is at the same time affected with measles and whooping-cough, or with whooping-cough and chicken-pox, etc. Most epidemies of whooping-cough begin in the spring or the autumn.

Symptoms. The period of incubation of whooping-cough is seven days. The local symptoms generally begin with the signs of bronchial catarrh (cough, râles), which extend, on an average, over two weeks, and constitute the preliminary catarrhal stage of whooping-cough. The true nature of the disorder is disclosed only when the catarrhal stage has passed over into the spasmodic or convulsive stage, which generally has an average duration of four weeks; occasionally, it is true, persisting for more than twice as long. In this stage the character of the cough is distinctive. The patients are generally at first conscious of a sense of tickling in the larynx or beneath the sternum, which they are incapable of resisting. Often the patients now grasp the nurse, or an object close at hand, for support during the paroxysm of cough. They also not rarely break out into tears. The actual coughing paroxysm begins with a deep, long-drawn crowing or whistling inspiration, which has been compared to the bray of an ass, whence the older name of "asses' cough" for whooping-cough was derived.

This deep inspiration is followed by a greater or lesser number of short expiratory efforts at cough, during which the child is wholly unable to breathe, and appears to be threatened with suffocation. Finally, another whistling, long-drawn inspiration takes placethe so-called reprise, or whoop-but which again is followed by numerous renewed efforts at coughing. Generally the paroxysm of cough does not cease until viscid mucus has been expelled from the larynx into the mouth, and which not rarely must be removed from the mouth of the little patients with the fingers.

During the paroxysm of cough signs of disturbances in the venous circulation make their appearance. The entire face and the skin of the neck acquire a bluish-red, cyanotic appearance, whence the name "blue cough," the jugular and the facial veins become distended into thick blue cords, the eyeballs protrude (exophthalmos), and the lips become greatly swollen, like sponges. Often the face, particularly the forehead, becomes covered with sweat. The duration of the individual paroxysm of cough varies between ten and thirty seconds, and but rarely persists for a longer time. The condition becomes especially distressing if one paroxysm of cough is immediately followed by a second and a third. In addition to the fear of suffocation the patient then suffers especially from pain in the head and vertigo, in consequence of intracranial circulatory disturbances.

The number of paroxysms of cough in the course of a day is extremely variable and determines the severity of the disease. In mild cases possibly from three to five seizures may occur, while in severe cases the number may be from sixty to one hundred, and even more, within twenty-four hours. After the termination of the paroxysm the patients usually recover with surprising rapidity, and soon resume their play with unaltered cheerfulness. The individual paroxysm of cough occurs either without exciting cause or in consequence of emotional disturbances, in laughing, or as a result of the entrance of foreign bodies into the larynx. Occasionally it can be induced by protrusion or by depression of the tongue. The paroxysms usually occur with greater frequency at night, because mucus readily accumulates in the larynx during sleep.

Examination of the bronchi and the lungs discloses either no alterations or signs generally of dry bronchial catarrh (sonorous) and sibilant râles). On the other hand, distinctive alterations will be found in the larynx and the trachea on laryngoscopic examination. Laryngoscopic examination in children is, it is true, generally attended with great difficulty. The laryngeal mucous membrane, down to the true vocal bands, will be found vividly reddened -particularly the region between the arytenoid cartilages (interarytenoid space), which responds with especial readiness with cough to mechanical irritation-and also the posterior surface of