34$ AGRICULTURAL BACTERIOLOGY. 



CHAPTER XV. 

 TUBERCULOSIS. 



OF all the strictly pathogenic bacteria there is none so widely 

 distributed as the B. tuberculosis. The great prevalence of 

 this disease in the human race has made the subject one of 

 the highest importance. Not only is it of great significance 

 from the standpoint of human health, but it is the one disease 

 of domestic animals which demands universal attention and 

 interest among agriculturists. Tuberculosis among cattle 

 forms one of the most vital subjects connected with modern 

 agriculture. 



THE TUBERCULOSIS BACILLUS AND ITS GENERAL CHARACTERS. 



The organism which produces this well-known disease has 

 been known to science about 18 years, having been first de- 

 scribed by Koch in an epoch-making monograph published in 

 1882. Professor 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 tuberculous. The organism itself appears com- 

 monly in the form of a short, slender rod (Fig. 39, r) about 

 .2 to .4 [JL in diameter and 1.5 /J. to 4/1 in length. It has no 

 motility and never forms long chains, although three or four 

 may frequently be seen together. 



In all questions concerning the distribution of an infectious 

 disease the formation of spores is of most vital importance, as 

 we have already seen. The problem of the formation of 

 spores in the tuberculosis bacillus stands upon a somewhat 

 uncertain footing. At times there have been seen within the 



