THE TUBERCLE BACILLUS 595 



lymphatics. Calmette believes that actual direct infection of the lung 

 by inhaled bacilli is relatively rare and bases this upon experimental 

 evidence. This, however, is not in agreement with the bulk of evi- 

 dence, and direct inhalation is probably the most common manner of 

 invasion. 



According to the researches of Bartel and many others, it appears 

 that direct infection through the apparently uninjured mucous mem- 

 brane of the intestinal tract may take place, and after such entrance the 

 bacilli may be carried by the lymphatics and blood to the lungs and 

 other parts of the body. Calmette states that, in all susceptible ani- 

 mals, man included, and in all its varieties of localization, tuberculosis 

 in the large majority of cases originates in a primary infection of the 

 lymphatics which takes its origin by entrance of the tubercle bacilli 

 through the mucous membranes of the digestive tract, chiefly the 

 mucous membranes of the mouth, pharynx and intestine. This is the 

 extreme view, but one that is favored in addition to Calmette by Von 

 Behring, Ravenel and others. 



Opie 25 as a result of recent studies, states that first infection with 

 tuberculosis may occur either by way of the lungs or the gastro-intestinal 

 tract, and the occurrence of one lesion tends to prevent the other. 



In man, tuberculosis is most common in the lungs where it usually 

 starts in the apices. The apical situation of early tubercles is not 

 entirely explained. A number of theories have been advanced, most of 

 them based on anatomical reasoning. In the lungs there may be a 

 miliary distribution of tubercles or, by coalescence of these, large 

 areas of consolidation may occur, which are then spoken of as phthisis. 

 Extension to the pleura is common. 



Although pulmonary infections constitute the very large majority 

 of cases of tuberculosis in adult life, this is not strictly true of childhood. 

 In statistics quoted by Calmette for Europe, it was found by Ham- 

 berger and Sluka 2G that of 160 cases in children there were only 50 per 

 cent pulmonary lesions. According to Dr. Holt's statistics for New 

 York, however, of 119 autopsies of tuberculous children, pulmonary 

 lesions were found in 99 per cent. In 1515 autopsies studied by 

 Comby during fifteen years, involvement of the tracheo-bronchial 

 lymph nodes was found in all. Aside from the pulmonary and 

 lymphatic infections, tuberculosis may occur in practically all other 

 parts of the body. 



23 Opie, Am. Kev. of Tuberculosis, vol. 4, 1920, p. 629. 

 26 Hamburger and Sluka, cited from Calmette, loc. cit. 



