TUBERCULOSIS 119 



prevention of tuberculosis were based on the assump- 

 tion that tuberculosis was caused by inhaling tubercle 

 bacilli. Later researches, however, showed that experi- 

 mental tuberculosis could also be produced in animals 

 by means of the ingestion of food impregnated with 

 tuberculous material or tubercle bacilli. When these 

 animals were autopsied they showed not only tubercu- 

 losis of the intestinal tract, but also tuberculosis of the 

 lungs. Also tubercles could commonly be found in the 

 lymphatic ducts passing from the intestinal tract to the 

 lymph glands of the lung. Von Behring in 1903 made 

 a great contribution to our knowledge when similar ex- 

 periments performed by him with very young animals 

 showed that when the tubercle bacilli were ingested 

 they might induce tuberculosis of the mesentary nodes 

 or of the bronchial lymph nodes without causing any 

 lesion in the intestinal tract. He stated as a hypothesis 

 that tuberculous infection in man would commonly 

 take place during childhood through the digestive tract 

 and that the tubercle baccili would lie dormant in the 

 bronchial lymph nodes for an indefinite period of time. 

 Skin infection was also proved to be possible though 

 rare. 



INFLUENCE OF THE BACILLI ON THE BODY. The 

 effect of the tubercle bacilli on the body, once having 

 entered it, depends upon a number of factors. These 

 factors are the initial number of tubercle bacilli, the 

 virulence of the bacilli, and the capacity of the body to 

 manufacture products which tend to wall off the bacilli 

 or to kill them. If the number of bacilli be relatively 

 small and the resistance of the individual good, the 



