72 THE AMERICAN BEAVER. 



the gland is also inflated, and shows large cells and 

 numerous septa. The constricted appearance of the 

 stomach is due to a triangular valve or septum pro- 

 jecting into its cavity. The upper part of the stom- 

 ach is doubled in, so that a triangular muscle ex- 

 tends across its cavity, its free margin measuring 2", 

 thus partially dividing the cavity into two portions. 

 A section of the stomach is represented in Fig. 6, 

 showing the triangular muscle and the gland. The 

 pylorus is muscular, and the orifice much smaller than 

 the duodenum. The intestine is twice the diameter 

 of the pylorus, and is doubled back upon the stomach. 

 In northern regions, and in winter, the beaver must 

 subsist either on wood or bark. The latter is com- 

 paratively innutritions. Besides, it would involve a 

 vast amount of labor on the part of the animal to 

 provide a winter stock of bark, which must be trans- 

 ported, together with its wood, to be submerged for 

 future use. The proportion of bark to wood, of the 

 kinds used by the beaver, is from to to g. This ques- 

 tion is settled by examining the aliment actually con- 

 sumed by the animal. The stomach has been found 

 distended with finely comminuted woody fibre, and 

 the same material was found in the colon. In another 

 case the contents of the stomach, partly filled, were 

 the same, weighing 1 lb. 3 oz. The masses in the 

 colon were of the same character. If bark were in- 

 gested with the wood it must have been in small 

 quantity. The conclusion, therefore, is that the 

 beaver derives its nutriment from the vegetable gum, 

 sugar, and albumen contained in the alburnum or 

 sap-wood, when it cannot obtain succulent roots and 

 vegetables. 



