CLASS MAMMALS: OEDEK UNGULATA. 



53 



of the slit, and so reaches the third stomach. Here it under- 

 goes further preparation and passes directly into the fourth 

 stomach, where the actual process of digestion is carried on. 

 The mechanism for conveying the unchewed mass in the 

 first stomach back into the mouth also depends upon the 

 lip-like tube. The contraction of the walls of the rumen 

 forces portions of the food into the reticulum ; in turn, the 

 contraction of its walls crowds a part against the outside of 

 the lips, which, opening, pinch ofE a portion, and, compress- 

 ing it into a ball, present it to the oesophagus, the fibres of 

 which, contracting successively from below upward, push it 

 forward into the mouth. 



The order can be tabulated into Families by a comparison 

 of their hoofs and horns : 



■« 

 fe 



3 



Perlssodactyl 



!TOE; 



THREE TOES ; 



Equids, 



( Bhinocerotidse, Rhinoceroe. 

 ( Tapiridee, 



Tapir. 



Camelidse.— Camels 

 have two toes, united 

 nearly to the point by 

 the callous sole. The 

 second stomach is used 

 as a receptacle for 

 water, the excess over- 

 flowing into cells along 

 the upper part of the 

 first stomach, which 

 the animal can open at 

 will, and supply the 

 moisture necessary for digestion 



Fig. 70. 



Skeleton of a Camel. 



