206 BACILLUS TUBERCULOSIS. 



Although it has been known since Koch's first studies in 

 tuberculosis that there was a slight biologic and morphologic 

 difference between the bacillus tuberculosis of man and that 

 of cattle, yet there was no doubt as to the identity of these 

 organisms. 



The bacillus of bovine tuberculosis is constant in its shape ; 

 it is shorter than the bacillus of human tuberculosis, and does 

 not exhibit the variations in form so frequently met in the 

 human variety. It stains more readily and evenly, although 

 occasionally it is seen to contain deeply staining bodies sug- 

 gestive of spores. It has been demonstrated experimentally 

 that it is much more virulent than the bacillus of tubercu- 

 losis in man. It produces extensive lesions and induces 

 rapid coagulation-necrosis. It grows more slowly in culture. 

 The tissue lesions are identical. 



Koch recently startled the medical world by claiming that 

 the bacillus of human tuberculosis and the bacillus of bovine 

 tuberculosis are distinct organisms, and that reciprocal infec- 

 tion never occurs. He based his claim on the finding that 

 injections of pure cultures of human tubercle bacilli into 

 cattle were not followed by a typical tuberculosis. Although 

 there are not many cases on record where tuberculosis in man 

 can be traced directly to cattle, there is no question that this 

 occurs. Cases of unquestionable primary intestinal tuber- 

 culosis, in an individual who is not tubercular, cannot be 

 explained in any other way than by assuming that the germ 

 was ingested with the food i. e. 9 beef. Tabes mesenterica in 

 artificially fed babies undoubtedly has its origin in the milk- 

 supply. Until more accurate studies can be made in this 

 direction it is advisable to regard bovine and human tubercu- 

 losis as reciprocally infectious diseases. 



Fowl Tuberculosis. 



The bacillus of fowl tuberculosis is morphologically sii 

 the bacillus of human tuberculosis. It is loner and sle 



similar 



to the bacillus of human tuberculosis. It is long and slender, 

 and frequently shows branching forms. It grows quite readily 

 on all culture-media. It stains like the bacillus tuberculosis, 

 but takes the stain more readily. Its principal distinctive 



