234 POPULAR SCIENCE MONTHLY 



In view of these facts, it is not surprising to find that Koch and Sehiitz 

 later failed to produce marked or general tubercular infection of cattle 

 by feeding or inoculating directly into the circulation tuberculous 

 materials and cultures of tubercle bacilli of human origin. That this 

 result does not dispose of the entire question at issue, but leaves open 

 the important consideration of the implantation of the more virulent 

 bovine bacilli upon man was, of course, present in Koch's mind, and 

 was met by him by emphasizing the infrequency with which primary 

 intestinal tuberculosis, which is the form of tuberculosis presumably 

 arising from ingested virulent tubercle bacilli, is encountered in human 

 beings. The reports which have appeared since have tended to show 

 that primary tuberculosis of the abdominal viscera, especially in chil- 

 dren, is not so infrequent as Koch believed it, and the researches in- 

 spired by Koch's address have brought out the important fact, now 

 based upon actual observation under the microscope, that tubercle 

 bacilli may pass through the intact intestinal wall and reach, by means 

 of the lymph current, the mesenteric glands; and have made it seem 

 probable, also, that by entering or being carried into the blood vessels 

 in the intestine the bacilli may be carried to the lungs. When all the 

 known facts of food infection in tuberculosis are assembled, they make 

 quite an imposing array, for they indicate, quite in opposition to the 

 exclusive view expressed by Koch, that tubercle bacilli entering the 

 body with food may be implanted upon the mucous membrane of the 

 mouth, from which, probabl}'', chiefly in the region of the tonsils, they 

 may be carried to the lymphatic glands of the neck and adjacent parts 

 where they develop and produce tubercular disease; or they become 

 implanted upon the intestinal mucosa and pass the epithelial barrier 

 without first causing disease there, and set up lesions in the mesenteric 

 lymph nodes or even be transported by the blood or lymph to the distant 

 lungs; or they may first multiply in the intestine, cause tubercular 

 disease there, and then migrate further, involving the abdominal and 

 thoracic organs. 



If I have seemed to tarry too long over this aspect of my subject, I 

 will ask you to consider for a moment in how far the endeavor to limit 

 the spread of tuberculosis among the human race must be influenced 

 by the avenues of infection to which the race is exposed. If we side 

 with Koch in the view expressed in 1901, and reiterated just the other 

 day in his Nobel-prize address, that, as he says, human tuberculosis 

 and tuberculosis in cattle are so distinct from each other that the latter 

 is not to be feared as transmissible to man, at least, as his last utter- 

 ance puts it, not in a form which comes in consideration in regard to 

 tuberculosis as a ' VollcskraiikheitS or race disease, then it is only 

 necessary to direct efforts to the suppression of tubercle bacilli of 

 human origin. For, if the danger of infection of surroundings and 



