TUBERCULOSIS. (continued 2)

Dog and Cat. The lesions are often concentrated on the respiratory or alimentary tract, but they have been noted also in the pharyngeal glands, tonsils, posterior nares, serosæ, liver, pancreas, spleen, nerve centres, ovary, uterus, testicle, epididymus, tunica vaginalis, prostate, heart, aorta, bones and joints. They follow the regular development of bovine tubercle, and caseation and cretefaction are prominent features. These animals are especially liable to infection by eating the left victuals from the plate of a consumptive owner, as well as by devouring consumptive prey, and the primary lesions are to be looked for along the line of the throat, bowels, liver and lungs. For the dog Cadiot records caseating polypi and ulcers on the mucosa of the larynx, trachea and bronchia, and Müller and Cadiot several cases of pharyngeal caseating adenitis in the dog bursting externally and developing intractable fistulæ, having abundance of bacilli in the discharge. These he attributes to expectorated virus from old standing tubercles in the chest infecting the pharyngeal mucosa and indirectly the lymph glands. The infection entering with the food and lodging in the follicles of the tonsils would act in the same way, and infected wounds received in fighting must also be quoted. Cats suffer from similar intractable sores, some of which may be traced to a tuberculous origin. The lungs are often extensively hepatized and of a general pale grayish color, but the early miliary lesions, the caseating and cutaneous centres, the vomicæ often intercommunicating, the tuberculous bronchial and mediastinal glands and the bacilli show the true nature. Intestinal ulcers are common, especially on the agminated glands, 441and small tubercles, in all stages of degeneration are met with in the enlarged liver, the spleen, pancreas, kidney, etc.

Apes and Menagerie Animals. In these tuberculosis is common alike in the thoracic and abdominal forms, and the lesions in the main are those of domestic cattle.

Chickens. The lesions are common in the abdominal cavity, the intestines, liver and spleen being the most frequently attacked, while the subcutaneous connective tissue, bones and joints also suffer. The lungs and kidneys usually escape. The intestinal mucosa shows small nodules, often caseated, or ulcers; the enlarged and friable liver is studded with tubercles from the size of a hemp seed upward, gray or translucid, homogeneous or with central necrosis, simply or in conglomerate masses, with congested or hæmorrhagic periphery; the spleen is swollen and permeated by similar deposits; fibrinous ascitis is not uncommon; the abdominal lymph glands are enlarged and congested.

The early tubercle shows a central, necrotic, hyaline area, consisting of the debris of disintegrated cells, which is colored brown by picro carmine, unlike the nucleus of the pheasant tubercle (Cadiot). Around the hyaline centre is a zone of large epithelioid cells, the nuclei of which stain strongly in carmine. Outside this is the usual zone of small, round, lymphoid cells. In the whole the tubercle bacilli can be made manifest by the carbol-fuchsin (Ziehl-Neelsen) stain. In the older and larger tubercles the central necrotic mass has encroached in part or in whole on the epithelio-lymphoid zone.

Pheasant. The lesions have the same seats and naked-eye aspect as the chicken tubercle, but under the microscope the smallest and most recent tubercles show epithelioid cells to the centre, or later, the central zone presents a dense fibrous network enclosing open spaces and giving a mahogany stain with Lugol’s solution (iodine and potassium iodide). (Cadiot). There has been an organisation of connective tissue which has submitted to amyloid degeneration, making a clear distinction from the tubercle of chicken.

Parrot. The lesions were thus located by Eberlein and Cadiot:

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Cadiot. Eberlein.

Eye and periocular region, 12 14

Commissure of the beak, 7 11

Tongue, 8 9

Palate, 4

Larynx, 2

Bones and Articulations, Upper limbs (wings), 7 14

Claws, 3

Cervical, Dorsal and Caudal, 5

Lungs, 7

Liver, 4

Intestine, 3

Muscles, 1

Heart, 1

The skin lesions are vascular neoplasms containing bacilli and usually invested with a covering of horn, but sometimes, on the legs and feet raw. The morbid growth may be rounded or conical, narrowing to a point. The lesions of the buccal mucosa begin as small, grayish swellings on the angle of the mouth, palate, tongue or larynx which grow out into more or less rounded vegetations. The lesions of the liver and lungs are mostly miliary with the usual tubercular features, but they may grow to larger size, as a pea or bean. In the cancelli of bones and on their surface, the lesions resemble those of the mammal.

The cutaneous form has been held to be the counterpart of warty lupus of man, the more plausibly that the disease is developed by inoculation from tuberculous men. The arthritic type represents what is described as gout in parrots.

In any case the recent miliary lesion presents the true tubercular type of a central giant cell or cells with bacilli, surrounded by epithelioid cells, and they in turn by small, rounded lymphoid globules.

PRIMARY AND SECONDARY INFECTION.

The estimate of the relative, early or late infection of two organs or tissues may often be made with reasonable accuracy from the fact that the lesions in one organ are old, caseated, calcified or sclerosed, while those in the other organ are all recent, with vascular environment and almost devoid of caseation or other degenerative process. We cannot safely predicate our decision on the greater number of old lesions in one organ rather 443than another, as the disease may have advanced much more rapidly in the one tissue. Still less can we state with certainty that the disease has not entered by a given channel because no lesions are left to show the transit of the bacillus along its supposed course. We frequently find tuberculosis of the bronchial or mesenteric glands, when we can detect no lesion in the lung, nor intestine. The bacillus has been passed on without establishing any lasting lesion in transit.

It is often too confidently asserted that the infected dust inhaled, falls directly on the air cells and determines the extensive pulmonary tuberculosis that ensues. So, on the other hand, it is often too arrogantly assumed that tubercle bacilli ingested with food, must necessarily show their results mainly in the intestines, mesenteric glands and liver. That solid particles can find their way directly into the lungs, has long been demonstrated by the pulmonary anthracosis of the miner, and the deadly phthisis of the stone hewer and cutler. The experiments of Cornet, Tappeiner and others in producing pulmonary tuberculosis, by compelling the inhalation of infected spray, corroborate this experience very satisfactorily. Yet it does not follow that all of the offensive matter penetrated the air cells at once on the air inhaled. The heavy particles of steel, quartz and even of coal dust must be mainly arrested on the surface of the moist air passages, yet, under the irritation caused by their presence and the consequent arrest of the ciliary motion, they would slowly gravitate downward to the pulmonary cells. In the case of the inspired tubercular spray or dust, we must recognize the possibility of the approach of the bacillus to the lungs through the lymph and blood channels as well. The bacilli lodged in the pharynx, and, above all, in the tonsillar follicles, can readily enter the lymph vessels, and are finally poured into the lower end of the jugular vein, but a few inches from the right heart, by which they are instantly propelled into the lungs. If then the lung is the most receptive and least resistant organ, it may easily be that this is the first point where the bacillus can establish a strong and effective colony. Apart from this the colonization of the tonsillar follicles may determine a constant supply of fresh bacilli, which may gravitate down with the abundant mucus toward the lungs.

444This tuberculous colonization of the tonsillar follicles is doubtless the main source of the infection of the pharyngeal lymph glands, which is so common in ox, pig and dog. It tends further to intestinal tuberculosis through the frequent swallowing of the products of the infected follicles. Then the infection of the pharynx and tonsils, whether established by inhalation or deglutition, may be the first step toward a secondary infection of the intestines.

Again the bowels can be infected by the frequent swallowing of the expectorations brought up from the diseased lungs or bronchia.

Conversely the lungs may be easily infected secondarily from preëxisting disease of the abdominal organs, and again primarily through the lymph channels. With tuberculosis of the cardia or liver the bacilli can follow the lymph vessels of the œsophagus or vena cava so as to reach the mediastinal glands, and from these glands in a state of disease they can easily pass into the adjacent pleural cavity and reach the lung. Or by following the mesenteric lymphatics they reach the thoracic duct and enjoy what is virtually for them a culture fluid, until discharged into the jugular, which, as already stated, is but a few inches from the right heart and lung.

Extension through the general blood stream usually takes place only when tubercles have already become numerous and extensive in a given region of the body, and its occurrence is the signal for a generalized tuberculosis.

The extension from the gastro-intestinal organs, pancreas and spleen may be considered as a partial exception. Here the infecting blood is not the general blood stream, but has to run the gauntlet of the liver capillaries by which the bacilli may be sifted out and delayed. This arrest subjects the liver to secondary tuberculosis in almost all cases of abdominal tuberculosis, and goes far to explain the extraordinary frequency of the disease in this organ. Ingestion tuberculosis almost necessarily leads to hepatic tuberculosis, and this notwithstanding that the primary lesion may have been very circumscribed.

The tuberculization of such a large vascular organ as the liver, however, paves the way for further extension, and if once extensively diseased, the early generalization of the infection is to be dreaded.

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