58 DISEASE IN WILD MAMMALS AND BIRDS 
of the ten cases show myocarditis. Nephritis does not 
seem very important in relation to cardiac muscular 
increase, but occurs with great frequency in association 
with dilatation. Three of the cases of hypertrophy were 
associated with thyroid disease and two of these showed 
dilatation as well. The general causes of chamber 
distention are more diverse, and we see associations 
that do not appear with hypertrophy, namely arterio- 
sclerosis and diseases of the chest. 
The rodents seem to have no power to increase muscle 
bulk, but a sufficient number of cases of dilatation occur 
to make one conclude that this is their method of response 
to unusual strain. Pulmonary disease, mostly of infec- 
tious nature, and myocardial degenerations are the 
principal causes. 
The next order to show cardiac enlargement is the 
Ungulata where nephritis is the most frequent associa- 
tion ^vith hypertrophy and disease of the pleura and peri- 
cardium with dilatation, or the reverse of the factor value 
in the Carnivora. These animals, fairly well prepared 
for flight, with moderately large hearts, seem more often 
to show dilatation than hypertrophy. 
Two Edentata (armadillo) showed dilatation but 
no hypertrophy. 
Marsupials behave somewhat like rodents in that the 
heart does not seem to increase muscle bulk, but our 
records do not explain this clearly. As already men- 
tioned four cases had no sufficient internal reason for 
dilatation, but as one was probably the result of shock 
three only remain to be accounted for. Nephritis seemed 
to exist in all three, but two of them had kangaroo-mycosis 
of the jaw and a general chronic infection. 
If now our attention be given to the Aves we find the 
highly specialized Passeres and Striges not represented 
and their closely related well-organized orders PicarisB 
and Psittaci with only an isolated single case. This is the 
more interesting since the last order suffers reasonably 
