250 FIRST LESSONS IN ZOOLOGY. 



sperm-whale will yield 2500 kilograms of this substance. 

 Another valuable substance is ambcrr/ris, a morbid product, 

 the result of injury to the intestine by the beaks of cuttle- 

 fishes, upon which animals the toothed whales largely prey. 



But the chief use of whales is the oil extracted from the 

 fat enveloping the body, called "blubber" by whalers. The 

 most valuable of the whales is the Greenland whale, as it 

 contains the most oil, individuals having been known to 

 yield nearly three hundred barrels. 



The Sea-cows. The manatee or sea-cow represents the 

 order of Sirenians; it is whale-like in form, but the teeth 

 and skull are quite unlike those of whales, while the man- 

 atee is herbivorous, the crowns of the teeth being flattened 

 and ridged as in the ox. 



The Elephants. The elephants are distinguished by their 

 colossal size, their tusks, and the large air-cells in the skull. 

 Another remarkable feature, from which the group takes 

 its name, is the trunk or proboscis, a long, thick, fleshy, 

 flexible snout, growing from the front edge of the nasal 

 bones. The trunk ends in a finger-like, highly sensitive 

 point, below which are situated the nostrils. In the ele- 

 phants the upper incisor teeth are enormously developed, 

 forming the tusks so characteristic of these animals, while 

 there are none in the lower jaw. There are no canine 

 teeth, while the few molars are large and transversely 

 ridged. 



In the nature of the limbs, especially from the fact that 

 elephants walk on their toes, a relation to the hoofed beasts 

 is indicated. They are usually five-toed, but the toes are 

 represented externally only by the five broad, shallow hoofs, 

 the foot being supported by thick, broad pads. The legs 

 are almost wholly free from the body. The skin is naked in 

 the existing elephants, but the extinct mammoth was cov- 

 ered sparsely with long hairs. Elephants live in herds, 

 browsing on the leaves of trees and herbs. They are rarely 

 over nine feet in height. The Asiatic elephant has a con- 

 cave forehead and small ears, while the African species has 



