364 THE BACILLUS OF TUBERCULOSIS 



with highly contaminated milk. It must, therefore, be considered 

 as established that man can be and is occasionally infected with 

 bovine tuberculosis and that tubercular cattle, particularly cows, are 

 not a negligible source of danger to man but one which warrants 

 measures to prevent the spread of tuberculosis from cattle to man. 



Avian Tuberculosis. There are certain differences in the morphology 

 and biology of the avian tubercle bacillus compared with the mam- 

 malian races. Microscopically it resembles, on the whole, the human 

 type rather than the bovine, but very often it shows considerable pleo- 

 morphism, with numerous coarse, club-shaped, and branched forms. 

 It grows more rapidly in artificial cultures than either the human or 

 the bovine type, and develops, in ten to fifteen days, round, moist 

 colonies, which grow rapidly and then form a continuous, dull-shining, 

 wax-like, fatty film over the surface of the medium, which later 

 becomes corrugated and assumes a decidedly yellow color. In its 

 moist character cultures of avian tubercle bacilli vary greatly from 

 the dry cultures of mammalian organisms. The latter do not grow 

 at temperatures over 41 C., while the former still multiply at temper- 

 atures between 45 and 50 C. Guinea-pigs are quite resistant 

 toward avian tubercle bacilli, but they sometimes contract the avian 

 disease in artificial inoculation and die from it. Rabbits appear to be 

 more susceptible to avian than to human tubercle bacilli. The horse, 

 according to Nocard, is susceptible to avian tubercle bacilli in artificial 

 infection. Chickens and pigeons are very susceptible and develop 

 the typical picture of avain tuberculosis. These birds are generally 

 not very susceptible to bacilli of human derivation, though some 

 observers have had positive results in inoculation experiments, and 

 it is also claimed that barnyard fowl have been infected from the 

 sputum of tubercular patients. Straus and Wurz and Nocard, how- 

 ever, have fed chickens for a long time on tubercular sputum without 

 producing the disease. Nocard implanted collodion sacs containing 

 human tubercle bacilli in the peritoneal cavity of chickens, and 

 succeeded in changing their morphologic and cultural characteristics 

 and their pathogenicity for chickens so that they became much like 

 the bacilli of avian tuberculosis. Mohler and Washburn investigated 

 an outbreak of tuberculosis among the fowl of a large ranch in 

 Oregon. This epizootic seemed to extend to the swine of the same 

 place, through feeding the hogs on the carcasses of fowl that suc- 

 cumbed to the disease. They found that young pigs could be infected 

 with tuberculosis by being fed material from tuberculous chickens 

 from this ranch, and that these avian bacilli, after a repeated passage 

 through mammals, would produce typical lesions of tuberculosis in 

 the latter. 



From the various observations quoted above it appears that avian 

 tuberculosis can be transmitted to mammals, and vice versa. It is, 

 of course, an established fact that parrots in captivity are quite 

 susceptible to tubercular infections from man. 



