RELATION OF BOVINE TO HUMAN TUBERCULOSIS. 
603 
solipeds, are usually contracted through the ingestion of con¬ 
taminated foods or water; but the morbid lesions are not con¬ 
fined to the digestive tract; in fact, it is the exception to find 
seats of the infection in these organs, especially in the latter 
disease. 
The question naturally arises, why should this theory apply 
to the tubercular bacillus so much more forcibly than to other 
organisms of a similar nature? Nor do laboratory experiments 
substantiate this theory as fully as we might reasonably 
expect. 
It should be borne in mind that in artificial inoculation the 
bacilli are usually introduced into the animal economy in very 
much larger numbers at a time than in natural infection. 
Is it beyond the limits of sound reasoning to suppose that if 
a large number of these germs are introduced at a given point 
that they will act as a foreign body that will produce more or 
less irritation, thereby forming a favorable nidus for the devel¬ 
opment of the germs and obstruct their entering the circulation ? 
Whereas, in natural infection the germs are usually so few in 
number as to produce little or no irritation to a free surface ; 
consequently, they would be much more likely to gain an en¬ 
trance to the circulatory system. Therefore, we should expect 
a much greater per cent, of development of morbid lesions at 
the point of entrance in artificial than in natural inoculation. 
My experience in post-mortem inspection leads me to believe 
that in cattle primary lesions of the lungs are comparatively 
rare. A careful necropsy will usually demonstrate that the 
primary focus or foci are in some of the lymph glands, and with 
these serving as extensive culture fields, from which the germs 
are carried to other parts of the animal economy by continuity 
of the parts and by the circulatory systems. This process of 
auto-infection, with probable reinfections from external sources, 
sooner or later results in extensive or generalized morbid 
lesions. 
In swine the lymph glands, spleen and the osseous tissue 
seem to be the most frequent seats of primary foci. 
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