TUBERCULOSIS - 163 
secondary seeding with the bacteria 
that have escaped from a primary 
focus through the circulation may be 
restricted to the cavity in which 
the first lesions developed. It 
seems better, therefore, to accept 
Ostertag’s views and classify local 
and generalized tuberculosis in ac- 
cordance with the nature of the lesions 
rather than their distribution in the 
body. 
The fact is worthy of consider- 
ation, that very often cattle killed 
after reacting to tuberculin do not 
show extensive distribution of lesions. 
Frequently animals are killed soon 
after infection has taken place, in 
which case the lesions are restricted 
to a single lymphatic gland or other 
organs. In other cases old lesions 
of considerable proportion are found. 
Diagnosis. Tuberculosis is diag- 
nosed by the symptoms, lesions, by 
finding the tubercle bacterium, and 
by the use of tuberculin. The sera 
tests thus far have not been satis- 
factory. 
Lesions. The lesions in tubercu- 
losis are usually sufficiently charac- 
teristic to enable a diagnosis to be 
made from the gross examination of 
the affected organs. There are cases, 
however, where they are atypical and 
a diagnosis cannot be made from 
their appearance. 
Etiology. In many cases the spe- 
cific bacterium may be found by 
Fic. 36. A PHOTOGRAPH OF A SHORT 
STRIP OF THE SMALL INTESTINE OF 
A COW SHOWING SEVERAL SMALL 
AND ONE LARGE TUBERCULOUS 
ULCERS (NATURAL SIZE). 
staining films made from the lesions with the ordinary tubercle stain.* 
In young lesions this is usually not difficult but in old ones it is often 
*4 method for staining tubercle bacteria. Stain the preparation with fresh carbol 
