THE COMMUNICABLE DISEASES 491 
cent, the massive caseous form. These large figures 
(equaling when combined 85 per cent.) coupled with the 
fact that only 12 per cent, of the total were fibroulcera- 
tive and 1.8 per cent, of the pearl type, would seem to 
indicate that the nodular and massive caseous processes 
are the lesions to be expected in wild animals. Further- 
more, if these nodular and caseous forms speak for recent 
infection or acuteness of the morbid process, it would 
seem that wild animals have a low tissue resistance 
to tuberculosis. It is a widespread belief, in some degree 
well supported, that a disease new to an animal species is 
highly fatal and that the survival of the race depends 
upon an active self-immunization or the survival of the 
pathologically least susceptible. If tuberculosis be a 
disease of civilization, these figures would suggest that 
it is absent in nature. As a further support of this idea 
it can be said that with the exception of two cases in 
ungulates, no fibroid tuberculosis, approaching the 
quiescent type as seen in man and rarely in domestic 
animals, was encountered. Very rarely calcareous 
deposits will be found in both simian and ungulate 
lesions but these need not indicate a tendency to general 
healing although at that place the process may be inac- 
tive. The bird uses considerable fibrous tissue in the 
construction of its tuberculous mass but fibrosis never 
masters the situation with the formation of scar tissue 
sufficient to wall off the process. Pearl disease, a fibro- 
caseous condition, is not a healing fibroid procedure and 
is, in our material, of no numerical significance. 
Visceral Distribution. 
The distribution of the morbid lesions in the viscera 
presents some interesting features. In the first place the 
data leave no doubt that the most susceptible tissue in 
the wild animal body is, as in the case of human and 
domestic animals, the lung. The susceptibility of this 
organ in the two classes is however a different matter 
