RODENTIA OR GNAWERS. 123 



body covered with spines or stiff bristles, and the tail short 

 or wanting. The skin of the back is so furnished with 

 muscles that the animal can assume nearly the shape of a 

 ball, presenting bristles on all sides. The European Hedge- 

 hog is smaller than a common cat. 



The Tenrecs or Centetidpe (Fig. 134), .are somewhat 

 similar to the Hedgehogs, but they have a slender body, 

 and they cannot so completely assume the form of a ball. 

 They inhabit Madagascar, and although in a tropical cli- 

 mate are said to pass three months of the year in a state 

 of lethargy. 



In the cool and cold regions there are many animals 

 that pass into a torpid condition during the coldest part of 

 the year, the season least favorable for securing food. 

 And while in this state their physiological conditions seem 

 to approximate those of cold-blooded animals. The Hedge- 

 hog and Bat fall into so deep a torpor that no sign of 

 breathing can be detected ; and in the Bat's heart the pul- 

 sations fall from 200 in a minute to 30 in a minute, dur- 

 ing torpidity. 



SUB-SECTION XII. 



THE ORDER OF RODENTIA OR GNAWERS. 

 This Order includes all mammalia which are specially 

 fitted for gnawing, as Rats, Mice, Dormice, Gophers, Bea- 

 vers, Squirrels, Porcupines, Agoutis, Chinchillas, Guinea 

 Pigs, Hares, etc. The name comes from the Latin rodere, 

 to inmw. Linnaeus called it the order of Glires, from the 



~ 



Latin ylis, a dormouse. The Rodents are mostly small 

 animals, the Beavers being the largest of all, with the sin- 

 gle exception of the Capybara (Hydrockcerus), an aquat- 

 ic rodent about three feet long and with a bulky body, 

 which is found along the. rivers in South America. 



