18 Prof. BuckraND on the Adaptation of the Structure 
of this class; but the variations in the Elephant correspond with one another 
in such a manner as mutually to compensate any inconvenience that might 
arise from them, and to produce a harmonious result: * mais dans le pares- 
seux chaque singularité d'organization semble n'avoir pour résultat que la 
foiblesse et l'imperfection, et les incommodités qu'elle apporte à l'animal ne 
sont compensées par aucun avantage." (Cuvier, Ossemens Fossiles, vol. v. Part I. 
p.73. He then proceeds to consider the Sloths, with respect to their pecu- 
liarities of organization, as producing slowness and debility. 
The skeleton of the Bradypus tridactylus, or Ai, as represented Pl. 4. Cuv. 
Oss. Foss. vol. v. Part II. affords proportions extremely anomalous and appa- 
rently defective; the arm and fore-arm taken together are almost double the 
length of the thigh and leg, so that when the animal goes on all-fours, he is 
obliged to drag himself upon his elbows; and if he attempted to stand erect 
upon his hind-feet, the entire fore-foot would still rest upon the ground: but 
the di never can stand upright, because his hind-feet are so ill articulated for 
walking, that they are unable to support the body in such a position; the 
pelvis also is so broad, and its cotyloid cavities, or sockets receiving the head 
of the thigh-bone, are so set back, that the thighs are kept at a distance, strut- 
ting outwards, and the knees can never approach one another. The length of 
the fore-legs embarrasses the animal in its attempts to walk, and its forward 
movements on the ground are made by fixing its claws on an object, and then 
dragging its body up to it. 
In the above descriptions, which are almost literally translated, the learned 
author seems to view the structure of this animal, as Buffon had done before 
him, in relation only to its defects, as ill adapted to the ordinary movement of 
quadrupeds in walking upon the ground : had he considered its peculiarities in 
relation to their perfections, with reference to the habit of the animal, living 
constantly upon trees, and coming to the ground only for the purpose of 
passing from one tree to another, in those rare cases where it cannot pass 
from tree to tree without descending, the consideration of this habit would at 
once have explained all the apparent incongruities of structure; and every or- 
gan which appears so anomalous and ill adapted for walking upon the ground, 
would have been found pre-eminently fitted to supply the wants and comforts 
of an animal destined to spend its life upon trees. 
