380 A MANUAL OF BACTERIOLOGY 



formations may be very large, but do not show nearly 

 such a disposition to caseation or suppuration as the 

 human lesions. Epithelioid cells form the major part 

 of the growth, and giant-cells are very infrequent. 

 Enormous numbers of bacilli may be present in the 

 tissues ; in places they may be so numerous and closely 

 packed as to form distinct masses or nodules. The avian 

 bacillus is similar in morphology and staining reaction to 

 the mammalian bacillus, but on cultivation and inocula- 

 tion various differences between the two races become 

 evident. Thus, mice and rabbits are easily infected with 

 the avian bacillus, but guinea-pigs are resistant. Fowls 

 and swine are rarely infected with human bacilli, but 

 swine are susceptible to infection with avian bacilli. 



The mammalian bacilli flourish best at about 37 C., 

 and growth ceases at 41 C., whereas the avian bacilli 

 thrive luxuriantly at 43 C., and the growth of the latter 

 on glycerin agar is much moister and more wrinkled and 

 often more pigmented than that of the former. By 

 cultivation on boric -acid agar and on eggs, etc., the 

 mammalian bacilli are stated to assume the characters of 

 the avian. 



Avian tuberculosis is of considerable practical import- 

 ance as attacking poultry and many other birds in 

 captivity. A few cases have been recorded in which the 

 bacilli cultivated from human cases were of the avian 

 type, and therefore probably derived from an avian 

 source of infection. Two types of tuberculosis also occur 

 in the horse one in which the lesions are chiefly abdo- 

 minal, in the other the lungs and bronchial glands are 

 most affected. Nocard states that the bacillus obtained 

 from the pulmonary variety is generally of the ordinary 

 mammalian type, while that of the abdominal one belongs 

 to the avian. 



Relation of human and bovine tuberculosis. It was 



