332 PATHOGENIC BACTERIA. 



The bacillus will grow at 42°-45° C. quite as well as at 

 37 C, while the growth of the mammalian tubercle 

 bacillus ceases at 42 C. Moreover, the temperature of 

 43 C. does not attenuate its virulence. The thermal 

 death-point is 70 C. Upon culture-media it can retain 

 its virulence for two years. 



The growth upon artificial culture-media is luxuriant, 

 and lacks the dry quality characteristic of ordinary 

 tubercle-bacillus cultures. As it becomes old a culture 

 of fowl-tuberculosis turns slightly yellow. 



Birds are the most susceptible animals for experimental 

 inoculation, the embryos and young more so than the 

 adults ; guinea-pigs are quite immune, or after inocula- 

 tion develop cheesy nodes, but do not die. Artificial 

 inoculation can be made in the subcutaneous tissue, 

 in the trachea, and in the veins, never through the 

 intestine. After inoculation the birds die in from one 

 to seven months. The chief seat of the disease is the 

 liver, where cellular nodes, lacking the central coagula- 

 tion and the giant cells of mammalian tuberculosis, and 

 enormously rich in bacilli, are found. The disease never 

 begins in the lungs, and the fowls which are diseased 

 never show bacilli in the sputum or the dung. 



Rabbits are-easily infected, an abscess forming at the 

 seat of inoculation, and later nodules forming in the 

 lung, so that the distribution is quite different from that 

 seen in birds. It is very probable that the bacillus occa- 

 sionally infects man. 



The bacillus stains like the tubercle bacillus, but takes 

 the stain rather more easily. The resistance to acids is 

 about the same. The possibility that this bacillus is de- 

 rived from the same stock as the tubercle bacillus is 

 strengthened by the experiments of Farmi and Saleano, 

 who succeeded in increasing its virulence by combining 

 it with glucose and lactic acid until it became fatal to 

 guinea-pigs. 



Bacillus Resembling the Tubercle Bacillus. — While 

 there can be little doubt that the bacilli of human, 



