498 THE TUBERCLE BACILLUS GROUP 
It is believed at the present time that the bovine and avian tubercle 
bacilli are distinct entities. 
The morphology of the avian tubercle bacillus and its staining 
reactions are quite similar to those of the bovine organisms, except 
that pleomorphism is more marked in the former, particularly when 
it is grown at 40° to 42° C. It forms no spores and no capsules, is 
non-motile and has no flagella. It grows more readily than either 
the human or the bovine strains; the addition of glycerin to media, 
while not essential, increases the luxuriance of the growth. On coagu- 
lated blood serum or agar after six to ten days the organisms appear 
as small white colonies with a waxy luster. X second transfer to arti- 
ficial media results in a more luxuriant growth which spreads and 
increases in luxuriance, eventually covering the whole medium. The 
growth is moist and may become slimy, differing markedly in this 
respect from the human and bovine types. The pellicle formed on 
broth cultures is less friable and more tenacious than that characteris- 
tic of the mammalian strains. The range of growth is from 35 to 45 
degrees; 40° C. is the optimum temperature, but development is luxu- 
riant at 37° C. An exposure of two hours at 65° C. usually fails to 
kill avian tubercle bacilli— but fifteen minutes at 70° to 72° C. is 
fatal. The organisms are very resistant to drying, remaining alive 
for several months both in cultures and in uncontaminated material 
from infected birds. Unlike the human or the bovine disease, avian 
tuberculosis may be transmitted as a congenital infection. Mohler 
and Washburn^ found that eggs laid by tuberculous hens may contain 
avian tubercle bacilli in the white of the egg. Birds are comparatively 
readily infected artificially, however, by injection of the organisms. 
Edwards- has infected hens with the excrement of infected birds. The 
liver and the spleen are the organs more commonly involved.^ 
Among laboratory animals rabbits appear to be more susceptible 
than guinea-pigs, although Edwards appears to have successfully 
infected several guinea-pigs with pure cultures of the organism. 
Moore"* was unsuccessful in causing the bacilli to multiply in guinea- 
pigs but observed that the animals frequently died of marasmus, 
apparently from the absorption of toxins from the bacilli; Mohler^ 
has induced infection in swine by feeding them the carcasses of tuber- 
culous hens. Himmelberger'^ has made the important obser\'ation 
that calves may be susceptible to infection with the avian tubercle 
bacillus. 
1 Ann. Rept. Bur. An. Indus., U. S. Dept. Agric, 1910, vol. 25. 
- Ontario Agric. College Bull., No. 123. 
3 De Jong: Ann. Inst. Pasteur, 1910, 24, 895. 
* Jour. Med. Res., 1904, 11, 521. 
^ Twenty-four Annual Report, Bureau of Animal Industry. 
6 Centralbl. f. Bakteriol., orig., 1914, 73, 1. 
