CLASS-BOOK OF ZOOLOGY. 41 



SECTION VII. 

 4th Order. — Gnawers : (Glires.) 



$ 136. The Gnawers are distinguished from the other 

 Orders of Mammalia by having four front teeth in both 

 jaws, which are separated from the grinders by a void 

 space, and no canine teeth. 



§ 137. The absence of canine teeth in this Order, is 

 an indication that they take their food from the vegetable 

 kingdom, as we see in the beaver, squirrel, porcupine, 

 hare, rabbit, etc. 



§ 138. An animal, which has four incisors in both 

 jaws, no canine teeth, a fiat compressed tail, and a glan^ 

 dulous follicle on the lower part of the body contain- 

 ing the castoreum, is called a Beaver, (Castor Fiber.) 

 The castoreum obtained from those glandulous pouches 

 of the Beaver, contains from two to three ounces, and 

 is much used in medicine ; but it must not be con- 

 founded with castor-oil, which is a vegetable production. 

 The Beaver is about four feet long, the tail included, of 

 a chesnut-brown color, weighs about fifty pounds, and is 

 found near the banks of rivers, in the most retired places 

 of Arkansas, Missouri, Michigan, Canada, and Siberia. 

 The Beaver is celebrated for his surprising instinct, ac- 

 cording to which he constructs his artificial dwellings. 

 He is, notwithstanding, very stupid, and shows no personal 

 industry nor attachment, when domesticated, though 

 always very gentle and peaceable. The Beaver is every- 

 where violently persecuted on account of the castoreum, 

 and its most precious fur, used by hatters and furriers. 

 Its tail is considered as good food. 



} 139. The Muskrat, (Ondatra Americana,) a native 

 of North America, is of the size of a rabbit, with reddish- 

 brown long fine hair, a long compressed tail almost bare, 

 and small glandulous follicles, containing a musky sub- 

 stance. The utility of the Muskrat consists only in its 

 skin, which is considered as good fur, and the down mud 

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