300 VERTEBKATE ANIMALS. 



In the absence of incisor teeth in the upper jaw, the lower 

 incisors bite against a callous pad of hardened gum. The 

 Camel tribe differs in its dentition from the above typical 

 formula, and certain exceptions likewise occur in the males 

 of some other forms, and in one or two other less important 

 instances. 



The stomach in the Ruminants is complex, and is divided 

 into several compartments, this being in accordance with their 

 mode of eating. They all, namely, " ruminate " or " chew the 

 cud ; " that is to say, they first swallow their food unmasti- 

 cated, and then bring it up again after a longer or shorter 

 period in order to chew it. This is effected as follows (Fig. 

 149) : The gullet opens at a point between the first two com- 



FIG. 149. Stomach of a Sheep, o Gullet ; r Rumen or Paunch ; h Honeycomb "bag or 

 Reticulwm ; p Many -plies or Psalteriwn ; a Abomasum or Fourth Stomach. 



partments or stomachs, of which the largest lies to the left and 

 is called the " paunch," while the smaller right cavity is called 

 the "honeycomb bag" (reticulum). The paunch (rumen) is 

 the cavity into which the food is first received, and here it is 

 moistened and allowed to soak for some time. After the food 

 has lain sufficiently long in the paunch, it passes into the 

 "honeycomb bag," where it is made up into little balls or 

 pellets, which are then returned, to the mouth by a reversed 

 action of the muscles of the gullet. After having been thor- 

 oughly chewed, and prepared for digestion, the food is now 

 swallowed a second time. On this occasion, however, instead 

 of passing into the paunch, the masticated food is conveyed 

 into the third stomach. This is known as the " many-plies 

 or "psalterium" because its lining membrane is thrown into 

 a number of longitudinal folds, like the leaves of a book. The 



