444 Veterinary Medicine. 



This tuberculous colonization of the tonsillar follicles is doubt- 

 less 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 

 preexisting 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 oesophagus 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 mesen- 

 teric lymphatics they reach the thoracic duct and enjoy what is 

 virtually for them a culture fluid, until discharged into the jugu- 

 lar, 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-iutestinal organs, pancreas and 

 spleen may be considered as a partial exception. Here the in- 

 fecting 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 exten- 

 sively diseased, the early generalization of the infection is to be 

 dreaded. 



