THE SLOTH 253 



three-toed sloth, the hand of which is a triple-hook, 

 formed of three digits (each armed with a long strong 

 claw), which answer to the three middle fingers of the 

 human hand. There are several varieties of the three- 

 toed sloth, but they all agree in one more exceptional 

 character, since no other beast whatever possesses it. 

 This is the possession of no less than nine bones, or 

 " vertebrae," in the neck. What may be the reason of 

 this strange peculiarity w^e are quite unable to con- 

 jecture. The ai is generally a silent animal, but an 

 individual in captivity is recorded to have emitted, w^hen 

 pulled away from a branch to which it was clinging, a 

 shrill note like that of some monkeys. The teeth of the 

 sloths are exceedingly simple in form, and there are none 

 whatever in the front of the mouth. There are usually 

 but five above and four below on each side, and only 

 in the unau is each first tooth prolonged beyond the 

 others. The stomach of these leaf-eating animals 

 is complex, reminding us of that of ruminating 

 animals. 



The windpipe of the ai does not pass straight down- 

 wards and backwards to the lungs as it does in all other 

 mammals. It is folded on itself in a coil as is often the 

 case in birds and reptiles. 



Such are the main points which may here be men- 

 tioned, with respect to the structure, appearance, and 

 habit of these South American beasts ; but what, after 

 all, are sloths ? They have sometimes been supposed to 

 be distant relations of the monkeys. They were for a 

 time thought to be so by the great Linnaeus, and the 

 modern distinguished French naturalist, De Blainville, 

 also so considered them. With their round heads and 

 long arms they may be said to possess a certain resem- 

 blance to some of the apes, but such resemblance is 



