1 10 



Vcrtebrata. 



especially in a large gland called the thymus, placed 

 in the thorax, or cavity of the chest, in front of the 

 heart. This fat is absorbed during the winter, and 

 the animal arises next spring lean and hungry. The 

 lemmings extend far north into the Arctic regions, 

 some having been captured at the winter quarters of 

 the 'Alert ' in 1875, in N. latitude 82. 



66. Order 12, Proboscidea (Elephants). No 

 groups of mammals appear more diverse from each 

 other, in size at least, than do the rodents and the 

 elephants, and yet the latter are structurally more 



FIG. 54- 



Skull of young elephant. 



22, the premaxillary bone, containing the root of the tusk k ; 15, nasal bone ; 

 7, tempora region: 26, zygomatic arch ; i, lower jaw; c, upper jaw. 



closely allied to the former than to any other order 

 of mammals. The elephants are the giants among 



