390 Analyses of Books. [May 



supply so little to them, and the different parts of their body seem 

 so much at varience with the laws of co-existence which we find 

 established throughout the rest of the animal kingdom, that we 

 might really believe them to be the remains of another order of 

 things, the living relics of that preceding state of nature whose ruins 

 we are obliged to search for in the interior of the earth, and that 

 they have by some miracle escaped the catastrophe which destroyed 

 the other species which were their contemporaries. The skeleton of 

 the Bradypus tridactylus, or Ai, says Cuvier, affords proportions 

 extremely anomalous, and apparently defective ; the arms and fore- 

 arms 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 is also so broad, and its cotaloid cavities so 

 set back that the thighs are kept at a distance, strutting 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. This is the unfavour- 

 able side of the subject. Dr. Buckland views it in a benevolent 

 light. The extraordinary length of the arm, and fore arm, so 

 inconvenient for moving on the earth, are of essential and obvious 

 utility to a creature whose body is of too great weight to allow it to 

 crawl to the extremity of the branches to collect the extreme buds 

 and youngest leaves which form its food ; these long arms, in fact, 

 perform the office of the instrument called u lazy tongs," whereby 

 the creature brings food to the mouth from a distant point without 

 any movement of the trunk. The structure of the arm fixed to the 

 shoulder by an universal joint admitting of rotation, and having at 

 the elbow two kinds of articulations which allow pronation and 

 supination, gives to the hand a power of moving in every possible 

 direction. The breadth of the pelvis and outward position of the 

 thigh bones, which are also broad and flat, the distance of the knees 

 from one another, and curvature of the bones of the leg, admirably 

 adapt these extremities of the animal to the purpose of clasping, and, 

 as it were, riding upon the trunks and branches of trees : A peculiar 

 condition of life was to be provided for, viz. that of a quadruped 

 which was to feed, to sleep, and in short, to dwell entirely upon 

 trees, for the succulent nature of its food renders it necessary to 

 descend to drink ; and if we look at the anomalous extremities of this 

 animal with a view to their use as instruments of continual suspen- 

 sion upon trunks and branches, the hind legs performing the double 

 office of adhesion and progression, and the fore legs the quadruple 

 function of adhesion, progression, prehension and defence, we shall 

 find each article of deviation from ordinary structure adapted to some 

 useful function in its peculiar economy, we shall find a new system 

 of machinery contrived and set together as it were on a new plan, 

 from old materials, (as machines of different functions may be com- 

 pounded from similar wheels, every motion having relation to some 



