Infection by Inhalation. 527 



partly with the food, into the digestive tract of guinea pigs, goats and 

 cattle. In the older animals, whose lymph glands, on account of their 

 less dense structure allow an easier passage of the bacilli the thoracic 

 organs were frequently found affected exclusively. Occasionally the 

 bronchial glands also were involved. The younger animals showed af- 

 fection of the mesenteric glands. In old animals bacilli could be found 

 in the lungs twenty-four hours after alimentary infection had been 

 produced, while in young animals they could not be demonstrated until 

 after the fifth day. Vallee obtained similar results by feeding infected 

 milk and by direct injection of the bacilli into the mesenteric glands. 

 Orth & Rabinowitsch got the same results from endorectal infection. 

 DeHaan injected tubercle bacilli into the stomach of a heifer and three 

 months later demonstrated a pronounced tuberculosis of the lungs and 

 pleura, but found the intestinal mucous membrane and its lymph fol- 

 licles intact. 



The experiments of Ravenel as well as those of Nicolas & Desco 

 demonstrated the rapid transmission of tubercle bacilli from the intes- 

 tine to the thoracic organs. They fed cultures in butter, warm water, 

 pastry and in soups. Three or four hours later bacilli were present in 

 the thoracic duct. Bisanti & Panisset demonstrated the presence of 

 tubercle bacilli in the blood five hours after they had been ingested. 

 Orth & Rabinowitsch injected an emulsion of bacilli into the rectum, 

 Oljcrwarth & Rabinowitsch injected the bacilli into the stomach of a 

 pig and in both instances the germs were afterwards found in the cir- 

 culating blood. 



That tubercle bacilli may and do pass through healthy mucous 

 membranes has been amply demonstrated on healthy animals by num- 

 berless feeding and inhalation experiments with material which was 

 mechanically and chemically innocuous. The experiments of Dobrok- 

 lonsky among others showed that the mucous membranes might remain 

 perfectly unharmed during this process (although Baumgarten, on the 

 other hand, holds that the mucous membrane always suffers by the en- 

 trance of bacilli into its lymph follicles, especially in the intestinal 

 mucous membrane). 



Although there is no doubt that an infection of the respira- 

 tory organs may follow an intestinal infection, or result from 

 one, the fact that the former are by far the most frequent 

 seat of primary disease must be explained by their greater 

 susceptibility. This is especially true of the lungs, thus ex- 

 plaining the fact that these organs, no matter what the mode 

 of infection, are usually more intensely involved than any 

 other part of the body. Occasionally we find the development 

 of an isolated tuberculosis of the lungs following the injection 

 of virus into the subcutis or into other remote organs. Thus 

 we may justly consider the lungs as far as infection with tuber- 

 culosis' is concerned, as a locus minoris resistentiae (Cohnheim, 

 Orth, Baumgarten, Bartel). In regard to the frequent affection 

 of the lymphatic glands it is significant that these constitute 

 a close filter for corpuscular elements, especially in young 

 animals, and that they arrest a considerable portion of tubercle 

 bacilli which are in the lymph stream, and which then in spite 

 of the bactericidal action of the lymph elements (Manfredi, 



