CHAPTER XVIUI 
TUBERCULOSIS 
Of all germ diseases there is none so widely distributed as 
tuberculosis. Not only is it of great significance from the stand- 
point of human health, but it is the one disease of domestic animals 
which demands almost universal attention and interest. Tuber- 
culosis among cattle forms one 
of the most serious problems of 
agriculture. 
Cause of the Disease.—The 
organism which produces this 
disease was first described by 
Koch in an epoch-making mono- 
graph published in 1882. Koch 
first isolated the bacterium 
= OP, YL . from thesputum of consumptive 
DO: &Z GP patients, and subsequently 
“ found it in abundance in an- 
Fic. 50.~—-Tuberculosis bacillus a, in 
a bit of animal tissue; 6, showing ir- 
regularities resembling spores; ¢, typical 
appearance of the bacilli: from ordinary 
imals suffering from certain 
diseases now known to be 
forms of tuberculosis. The 
cultures. 
organism itself appears com- 
monly in the form of a short, slender rod (Fig. 50). Although 
commonly called Bacillus tuberculosis, it cannot properly be 
called a Bacillus since it possesses no flagella* (see page 14). 
Although this organism does not form spores, it has a consider- 
able resistance against heating and even drying. It may be dried, 
* Recent studies have shown that the organism may show branching which is 
not the case with any true bacteria. It has been suggested that it should be placed 
in a special family named Mycobacteriacee. 
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