632 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
with established fact and not hypothesis, he had long been anticipated. 
That cattle are highly resistant to infection with tuberculous material 
and tubercle cultures obtained from human subjects can be concluded 
from the early experiments of Baumgarten, Sidney Martin, Frothing- 
ham, and Dinwiddie. The most conclusive evidence upon this subject 
is contained in Theobald Smith’s paper of 1898, in which he sum- 
marizes his experiments by stating that “ putting all the facts ob- 
tained by experiments on cattle together, it would seem as though the 
sputum bacillus can not gain lodgment in cattle through the ordinary 
channels.” In view of these facts, it is not surprising to find that 
Koch and Schiitz later failed to produce marked or general tubercular 
infection of cattle by feeding or inoculating directly into the circula- 
tion 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 tu- 
berculosis 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 children, is not so infrequent as Koch believed it, 
and the researches inspired by Koch’s address have brought out the 
important fact, now based upon actual observation under the micro- 
scope, 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 car- 
ried into the blood vessels in the intestine the bacilli may be carried 
to the lungs. When all the known facts of food infection in tubercu- 
losis are assembled, they make quite an imposing array, for they indi- 
‘ate, 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, probably, 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 pro- 
duce 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, 
1 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 in- 
fluenced by the avenues of infection to which the race is exposed. 
