Bovine Tuberculosis 749 



Staining. The bovine bacillus usually stains homoge- 

 neously; the human bacillus commonly shows the so-called 

 " beaded appearance." 



Vegetation. The human bacillus grows upon dogs' serum 

 much more luxuriantly and rapidly than the bovine bacillus. 



Metabolic Products. An important variation in the 

 metabolism of the human and bovine tubercle bacilli has been 

 pointed out by Theobald Smith,* who observed that cultures 

 of the two organisms upon glycerin bouillon differed in the 

 induced reaction of the media. The cultures of the bovine 

 bacillus tend toward neutrality, those of the human bacillus 

 toward acidity. This chemical difference is an adjunct to- 

 our means of differentiating the two organisms. 



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. 



(c) Cattle. Cows and heifers receiving intrapleural 

 and intra-abdominal injections of the human bacilli usually 

 gain in weight and show no symptoms. When examined 

 postmortem, circumscribed chronic lesions were found. 

 Those inoculated with the bovine bacillus lose weight, suffer 

 from constitutional symptoms, and show extensive lesions 

 at the necropsy. Two-thirds of the cattle inoculated experi- 

 mentally with the bovine bacillus die. 



Lesions In general the lesions produced by the bovine 

 bacillus were rapid, extensive, and necrotic. Many bacilli 

 are present. Those produced by the human bacillus are 

 more apt to be productive, chronic, and contain relatively 

 few bacilli. The bacilli of human tuberculosis produce lesions 

 with many giant cells; those of bovine tuberculosis, lesions 

 with rapid coagulation necrosis. The lesions resulting from 

 the intravenous injection of human bacilli into rabbits re- 

 sembled those observed by Prudden and Hodenpyl f after the 

 intravenous injection of boiled, washed tubercle bacilli. 



* "Trans. Assoc. Amer. Phys.," 1903, vol. xvm, p. 109. 

 f "New York Med. Jour.," June 6-20, 1891. 



