64 DISEASE IN WILD MAMMALS AND BIRDS 
greater in small and young animals than in large and 
adult ones. All the authors quoted agree that in birds 
and to less degree but still clearly in mammals, there is a 
direct relationship between the bodily activity of an 
animal and its cardiac bulk. This is fairly well shown 
in the list of avian heart ratios, but not so clearly in the 
mammals. What shall be considered the most active 
mammals — the monkey, perhaps, with his tendency to be 
occupied constantly, yet we find the greatest heart bulk 
among the Carnivora, animals prepared for travel and 
struggle, and the smallest among the Rodentia, quiet and 
timid animals. The avian order showing the greatest 
cardiac ratio, the Fulicarije, shore birds, is made up of 
some quiet hiding varieties, and of some capable of very 
prolonged flight; the most constantly active fliers (Pas- 
seres) also have a high cardiac weight proportion. The 
inactive owls have the smallest heart bulk. 
The contrast between the average heart-to-body 
weights of mammals and birds is striking, the latter hav- 
ing two and one-half times as much as the former, 
5.8 vs. 13.8. Since this is the most prominent and best 
supported statement in the table of weights, it may be 
used to compare vdth the incidence of the pathology as 
seen in the two classes. 
Degenerations and inflammations occur in mammals 
and birds as 9.5 is to 5.5.(7) 
Hypertrophies occur in mammals and birds as 10.3 is 
to 4.3.(7) 
Dilatations occur in mammals and birds as 2.4 is 
to .28.(7) 
In other words, mammals are much more susceptible 
than birds to degenerative and inflammatory processes, 
show an ability to increase the muscle bulk two 
and a half times as great and are liable to chamber dis- 
tention nearly ten times as often. It might also be put 
( 7 ) These figures are obtained by determining mathematically the 
percentage of each feature in each class and then reducing the numbers 
to their lowest value. 
