_In the peritoneum_ tubercle appears usually in the miliary form, leading sometimes to such extensive involvement of and interference with visceral functions as to produce anasarca or more general disturbance prior to death. Acute miliary disease here is as rapid and as essentially fatal as the same affection of the dura or pia, while the more chronic forms are followed by degenerations that may involve the intestines either in agglutinated masses or in ulcerations and possible perforations. The indication in all tuberculous lesions of serous membranes is for exposure by operation, disinfection of the surface, and evacuation of retained fluids. Recovery from tuberculous peritonitis, even of acute type, after abdominal section, is now definitely established as a possibility. The same would probably be true of tuberculous meningitis were we permitted to expose the membranes and attack them or drain them in the same way. Although a few distinct organs or tissues have here been specifically considered in their relations to tuberculous disease, there is no organ or tissue in the body which is exempt from its ravages and in which evidences of tuberculous disease may not be found. Even the _mammary gland_ occasionally presents tumors composed of tuberculous granuloma which more or less simulate malignant disease, while calling for the same radical treatment (Fig. 22). [Illustration: FIG. 22 Gross appearance in tuberculosis of the mamma. (Dubar.)] =Paths of Infection.=--The tuberculous virus may enter the body through various channels. Probably in the majority of instances it gains entrance through the _respiratory tract_, less often by the _alimentary canal_, and _occasionally by air contact of open wounds or direct infection by local agencies_. It is now well established that tuberculous disease is easily inherited, although a predisposition to its ravages is transmitted from parent to children.