252 CLASS MAMMALIA. 



The Sloths (Bradypus, L.), 



Have cylindrical molars and sharp canine teeth, 

 larger than the cheek-teeth ; two mammae on the 

 breast ; and fingers united together by the skin, and 

 marked outwardly only by enormous compressed 

 nails, always bent toward the inside of the hand and 

 the sole of the foot. Their hind feet are articulated 

 obliquely on the leg, and lean only on the external 

 side ; the phalangers of their toes are articulated by 

 a close ginglymus, and the first become attached at a 

 certain age to the metacarpian or metatarsian bone, 

 which also become in time attached to each other 

 for want of use. To this inconvenience in the or- 

 ganization of the extremities is joined another, not 

 less considerable, in their proportions. Their arms 

 and fore-arms are much longer than their thighs 

 and legs, soth at when they walk they are obliged to 

 draw themselves along on their elbows. Their basin 

 is so large, and their thighs directed so much on the 

 sides, that they cannot approximate the knees. Their 

 locomotion is the natural effect of so disproportioned 

 a structure*. They live in the trees, and never 

 quit one until they have completely stripped it of all 

 its leaves, so painful is it to them to mount another. 



* Mr. Carlisle has observed, that the arteries of the limbs com- 

 mence by infinite ramifications, which finally unite into one, from 

 which the ordinary branches proceed. This structure being found 

 also in the Loris, whose walk is not less slow, it is possible it may 

 have some influence on slowness of motion. The Loris, the Orang- 

 otang, the Coaita, all very slow animals, are all remarkable by the 

 length of their arms. 



