" The inoculation was effected by making a small incision in the abdominal wall of a guinea-pig with the scissors, inserting the point of the scissors to form a pocket-like subcutaneous wound, about half a centimetre deep. Into this little pocket a fragment of the inoculation substance about the size of a millet or mustard-seed was pushed as deeply as possible. On the following day the inoculation wound was always united, glued together, and showed no reaction. Generally it was not till after a couple of weeks that a visible swelling of the lymphatic glands next the seat of inoculation occurred, usually the inguinal glands on one side, and at the same time induration and the development of a nodule took place in the inoculation wound, which up till then had remained perfectly healed. After this the lymphatic glands enlarged rapidly, frequently to the size of a hazel-nut. The nodule at the seat of inoculation then generally broke and became covered with a dry crust, beneath which was a flat ulcer with a cheesy floor discharging very dightly. The animals began to lose flesh about this time, their coat became bristly, dyspnoea set in, and they died generally between the fourth and eighth weeks, or they were killed within the same space of time".

Tuberculosis has been induced or observed in nearly all the commoner warmblooded animals, and according to Koch no bird or mammal is capable of permanently resisting infection. Animals show, however, very different degrees of susceptibility, and in similar degrees they are variously liable to spontaneous tuberculosis. Babbits, guinea-pigs, cattle, and apes are peculiarly susceptible.

Carnivorous animals are much less so, but according to Macfadyean (Brit. Med. Jour., 1891, II., 1173), spontaneous tuberculosis is more common in dogs than is commonly supposed. In any given class of animals the individuals show varying susceptibility just as in the case of man.

The infective character of tuberculosis is also to be inferred from the spreading character of the lesion, to be now described.

Contagiousness Of Tuberculosis

As the tubercle-bacillus from its mode of growth is propagated only in the animal body, except as a laboratory experiment, the disease must be contracted more or less directly by contagion. According to Cornet the great source of contagion is the dust formed when tuberculous products, and especially the sputum of phthisical persons, is allowed to become dry and is pulverized. This author asserts that even strong persons are susceptible when exposed to such dust. It is thus by an intermediate process that infection usually occurs. Direct infection is rare. One of the most obvious cases of the latter is afforded by the chronic thickenings or warts to which pathologists are liable from infection at post-mortem examinations.

It is apparent that if the bacillus could be entirely got rid of in the community the disease would necessarily cease. This can only be effected by a system of isolation along with disinfection of discharges. The facts that about one-seventh of the deaths in the community are due to tuberculosis, and that probably not less than one-half of the persons born are fated to acquire the disease in some form, ought surely to justify such precautions. In this connection it is of importance to note that leprosy, under a system of rigid isolation, almost disappeared from Europe, and this surely affords a presumption in favour of similar precautions in the case of tuberculosis, which however can be carried out without any such cruel seclusion as in the case of lepers.

Inheritance Of Tuberculosis

While inheritance plays a very important part in the predisposition to tuberculosis, it has not yet been proved that, in man, tuberculosis is ever communicated from parent to offspring, although there are a few cases recorded in infants which may have been congenital. This-is consistent with the fact that the bacilli do not readily pass through membranes. Johne has recorded a case of congenital tuberculosis in a calf whose mother was affected with severe tuberculosis of the lungs. In the calf the tuberculosis was situated in the liver, portal glands, and bronchial glands, the infection having been by the umbilical veins in the placenta. (Referred to by Birch-Hirschfeld).