336 



VERTEBRATE AXIMALS. 



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 excep- 

 tions 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 unmasticated, and then bring it 

 up again after a longer or shorter period in order to chew it. This 

 is effected as follows (fig. 242) : The gullet opens at a point between 

 the first two compartments or stomachs, of which the largest lies to 

 the left and is called the " paunch," whilst the smaller right cavity is 

 called the "honeycomb bag" {reticulum). The paunch {nunen) is 



Fig. 242.— stomach of .a Sheep, o Gullet ; r Mumen or paunch : 7i Honeycointi bag or 

 reticulum ; p Many-plies or psalterium ; a Abomasura or fourth stomach. 



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

 tened and alli iwed to soak for some time. After the food has lain suf- 

 ficiently long in the paunch, it passes into the " honeycomb bag," 

 from which it is ultimately returned in successive portions to the 

 mouth by a i-e versed action of the muscles of the gullet. After 

 having been thoroughly 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 '^ pmlteriutn," 

 because its lining membrane is thrown into a number of longitudi- 

 nal folds, like the leaves of a book. The psalterium opens by a wide 

 aperture into the fourth and last stomach, known as the " abomasum." 

 This is a cavity of considerable size, which secretes the true digestive 

 fluid (gastric juice), and it is here that the food is really digested. 



