404 



Wished in all the rest of the animal kingdom, that one might really be- 

 lieve that they are the remains of another order of things, the living 

 relicts of that pre-existing state, whose other wrecks we can only dis- 

 cover in the interior of the earth ; and that they have escaped by some 

 miracle from those catastrophes which have destroyed their cotemporary 

 species. 



In this animal, the result of every singularity of organization seems to 

 be only weakness and imperfection ; and the inconveniencies which they 

 occasion to the animal seem not to be compensated by any advantage. 

 The name of the animal is derived from the plaintive cry which he 

 makes whilst moving, it sounds like the word Ai, and is repeated six 

 times in- an ascending musical series. 



A single glance at the proportions arid the singular structure of par- 

 ticular parts of the A'i (Bradypus Tridactylus, Linn.) will sufficiently 

 evince the propriety of these remarks. The arm and fore arm, taken 

 together, are nearly twice as long as the leg and thigh ; so that when 

 the animal would walk on all four, it is obliged to trail along on its 

 elbows. The pelvis is so wide, and the cotyloid cavities turned so back- 

 wards, that it cannot bring the knees together, but is obliged to keep the 

 thighs wide asunder. Animals, in general, receive their chief impulse 

 from the hind feet; good runners, as hares, having their hind feet long: 

 but the long fore feet can only serve, as in the crab, to impede their pro- 

 gress : hence the sloths can only employ them to cling by, and to draw 

 after them the hinder parts of their bodies. 



This extremely wide pelvis differs from that of other animals, in the 

 os sacrum having a second union with the other bones of the pelvis ; it 

 being joined with the tuberosity of the ischium, and thereby leaving 

 only an opening instead of the great ischiatic notch. This latter struc- 

 ture is only observable in Didelphus ursina, of Shaw. 



In the articulation of the hind feet, it appears as if it was intended to 

 prevent the animal from having any power of using them. Instead of 

 the articulation with the astragalus being a ginglymus, allowing the foot 



