CHAT GHEE: I 
STRUCTURE AND PRESENT DISTRIBUTION OF THE MAMMALIA 
External Form.—It would be quite impossible for any one to 
confuse any other quadrupedal animal with a mammal. The 
body of a reptile is, as it were, slung between its limbs, like the 
body of an eighteenth century chariot between its four wheels; 
in the mammal the body is raised entirely above, and is 
supported by, the four limbs. The axes of these limbs too, as a 
general rule, are parallel with the vertical axis of the body of 
their possessor. There is thus a greater perfection of the 
relations of the limbs to the trunk from the point of view of a 
terrestrial creature, which has to use those limbs for rapid move- 
ment. The same perfection in these relations 1s to be seen, it 
should be observed, in such running forms among the lower 
Vertebrata as the Birds and the Dinosaurs, where the actual 
angulation of the limbs is as in the purely running Mai- 
malia. These relations are of course absolutely lost in the 
aquatic Cetacea, and not marked in various burrowing creatures. 
The way in which the fore- and hind-limbs are angulated is 
considerably different in the two cases. In the latter, which 
are most used and, as it were, push on the anterior part. of 
the body, the femur has its lower end directed forwards, the 
tibia and the fibula project backwards at the lower end, while 
the ankle and foot are again inclined in the same direction as 
the femur. With the fore-limbs there is not this regular 
alternation. The humerus is directed backwards, the fore-arm 
forwards, and the hand still more forwards. This angulation 
seems to facilitate movement, inasmuch as it is seen in even the 
Amphibia and the lower Reptiles, in which, however, the differ- 
ences between the fore- and hind-limbs are less marked, indicat- 
