CHAPTER XVIII. 

 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. 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 



