18 Prof. BucKLAND 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 singularity d'organization semble n'avoir pour r^sultat que la 

 foiblesse et I'imperfection, et les incommodit^s qu'elle apporte a I'animal ne 

 sont compensees par aucun avantage." {Cuvier, Ossemem FossUes, vol. v. Part I. 

 p. 73.) He tlien proceeds to consider the Sloths, with respect to their pecu- 

 liarities of organization, as producing slowness and debility. 



The skeleton of the Bradypm trldactylus, or At, as represented PI. 4. Ciw. 

 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 Ai 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 ai-e made l^y 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 incongi-uities 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. 



fei 



