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which we find established in all the rest of the animal kingdom, that 
one might really believe that they are the remains of another order 
of things, the living relicts of that pre-existing state, whose other 
wrecks we can only discover 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 inconveniences which 
they occasion to the animal seem not to be compensated by any ad- 
vantage. The name of the animal is derived from the plaintive cry 
which he makes whilst moving, it sounds like the word A'i, and is 
repeated six times in ascending musical series. 
A single glance at the proportions and the singular structure of 
particular parts of the A'i ( Bradypus Tridactylus, Linn.) will suffi- 
ciently 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 
backwards, 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 progress ; 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 Dulelphus ursinci, 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 
