614 PATHOGENIC MICROORGANISMS 



of course, attaches to the question as to whether the bovine and the 

 human disease are mutually intercommunicable. This has been dis- 

 cussed in the preceding section dealing with the human type. 



Summary of the Differentiation between Bovine and Human Tubercle 

 Bacilli. Morphologically the bovine bacillus is a little plumper and 

 thicker than the human type, but this cannot be regarded as suf- 

 ficiently constant to be reliable for differentiation. On glycerin broth, 

 the final reaction in the case of human bacilli is considerably acid, the 

 final reaction with the bovine is very slightly above the neutral 

 point. The bovine bacillus does not grow as readily as the human 

 and is not aided by the addition of glycerin to the media to the same 

 extent as the human. The growth of the human bacillus is apt to be 

 more luxuriant than that of the bovine, especially in earlier generations. 



As to virulence, the bovine is much more virulent for all the ordinary 

 laboratory animals than is the human. The difference is particularly 

 marked in rabbits. Small doses of human bacilli inoculated into rab- 

 bits will kill them very late, and if quantities of less than 0.1 of a milli- 

 gram are used intravenously, the rabbits may live for longer than two 

 months, or may survive. Similar injection of the bovine type into 

 rabbits kills with greater regularity and more extensive lesions, usually 

 within two months. 



The Bacillus rf Avian Tuberculosis. A disease resembling in many 

 features the tuberculosis of man is not uncommon among chickens, 

 pigeons, and some other birds. Koch was the first to discover in the 

 lesions of diseased fowl, bacilli much resembling Bacillus tuberculosis. 

 It was soon shown, however, by the studies of Nocard and Roux, 78 

 Mafucci, 79 and others, that the bacillus of the avian disease represented 

 a definitely differentiate species. 



Morphologically, and in staining characteristics, the bacillus is 

 almost identical with that of the human disease. In culture, however, 

 growth is more rapid and takes place at a temperature of 41 to 45 C. 80 

 (the normal temperature of birds), while the human type is unable to 

 thrive at a temperature above 40. 



The organisms grow more easily than do either the human or bovine 

 bacilli. Colonies appear, on glycerin agar within a week and cultiva- 

 tion may also be successful on media without glycerin. It is char- 



ts Nocard et Roux, Ann. <le 1'inst. Pasteur, 1887. 

 Mafucci, eit. f. Kyg., xi. 

 80 Mafucci, loc. cit. 



