Bovine Tuberculosis 387 



tuberculosis. The conclusion that they are identical seems 

 inevitable, but in his monograph upon tuberculosis Koch 

 called attention to certain morphologic and cultural differ- 

 ences that exist between bacilli obtained from human and 

 from animal tuberculosis. Unfortunately, very little atten- 

 tion was paid to the subject until recently. 



It has not yet been determined that any other difference 

 exists between the two bacilli than can be accounted for 

 upon biologic grounds, each organism being modified to 

 accommodate itself to its environment. 



Though* occasional desultory experiments were made 

 from time to time, the subject seems to have met its first 

 thorough study at the hands of Theobald Smith,* who care- 

 fully compared a series of bacilli obtained from human 

 sputum with another series obtained from cattle, horses, 

 hogs, cats, dogs, and other animals. 



His observations form the foundation of the following 

 description of the bovine tubercle bacillus : 



Morphology. The size of the bovine bacillus is quite 

 constant, the individuals being quite short (1-2 //). They 

 are straight, not very regular in outline, and sometimes 

 of a spindle, sometimes a barrel, and sometimes an oval 

 shape. The human bacilli, on the other hand, are prone to 

 take an elongate form under artificial cultivation. 



Staining. The bovine bacillus usually stains homogen- 

 eously ; the human bacillus commonly shows the so-called 

 "beaded appearance," and is more apt to contain rounded, 

 deeply staining bodies suggestive of spores, at or near the 

 ends. 



Vegetation. The human bacillus grows upon dog's 

 serum much more luxuriantly and rapidly than the bovine 

 bacillus. 



Pathogenesis. (a) Guinea-pigs. The bovine bacilli are 

 more virulent than those of human tuberculosis, intraperi- 

 toneal inoculation of the former producing death in adult 

 animals in from seven to sixteen days ; of the latter, in from 

 ten to thirty-eight days. Subcutaneous inoculation of the 

 bovine bacillus causes death in less than fifty days ; of the 

 human bacillus, in from fifty to one hundred days. 



(b) Rabbits. Rabbits inoculated into the ear vein with 

 the bovine bacillus die in from seventeen to twenty-one days. 

 Those receiving human bacilli sometimes live several months. 



* " Trans. Assoc. Amer. Phys.," 1896, xi, p. 75, and 1898, xm, p. 417. 



