CHAPTER XVIII. 
TUBERCULOSIS. 
Of all germ diseases there is none so widely distributed as 
tuberculosis. Not only is it of gre_at significance from the stand- 
point of human health, but it is the one disease of domestic animals 
which demands almost universal attention and interest. Tubercu- 
losis 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 monograph 
published in 1882. Koch first 
isolated the bacterium from the 
sputum of consumptive patients, 
and subsequently found it in 
abundance in animals suffering 
from certain diseases now known 
to be forms of tuberculosis. The 
organism itself appears com- 
monly in the form of a short, 
slender rod (Fig. 51). Although 
commonly "called Bacillus tuber- 
culosis, it cannot properly be 
called a Bacillus, since it pos- 
FiG. 51. Tuberculosis bacillus, a, in a 
bit of animal tissue; b, showing irregu- 
larities resembling spores; c, typical ap- 
pearance of the bacilli from ordinary cul- 
tures. 
sesses no flagella.* (see page 
12). Although this organism 
does not form spores, it has a 
considerable resistance against heating and even drying. It may be 
dried, and yet remain alive for months, without losing its power of 
* 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 Myxobacteriae. It will 
doubtless retain the name B. tuberculosis. 
261 
