58 Mmnmalia. 



DIGESTIVE SYSTEM Gbneeal. 



The Digestive Apparatus in this Class is of varied complex- 

 ity ; but in almost all Orders are to be found a Mouth, Tongue, 

 Salivary Glands, Teeth, (Esophagus, Stomach, Small Intes- 

 tine, Liver, Pancreas, Spleen, and Large Intestine (the com- 

 mencement of which is commonly marked by a Caecum). Of 

 these we shall treat in order. 



The Mouth is almost always terminal, and bounded by fleshy 

 lips; these form the main characteristic of the Manmaalian 

 Mouth, inasmuch as the act of sucking is characteristic of all 

 young Mammalia, and this cannot be performed without 

 definite lips. The Lips admit of various modifications, 

 especially in the Quadrupeds, in which they are the main 

 agents in the prehension of food : the upper lip is generally 

 entire, but frequently marked with a median groove. The 

 Gape of the mouth is of variable width, but is rarely so small 

 as to admit only of the mere protrusion of the tongue. In 

 most Mammalia the Side Walls of the mouth are dilateable 

 and contractile, and Cheek Pouches are sometimes found 

 (chiefly in species of Insect-diet) : the Buccal membrane is 

 commonly smooth ; though sometimes beset with hard tuber- 

 cles. The Palate is usually more or less ridged transversely, 

 and the Velum palati* scooped out into a semilunar form, the 

 Uvulaf being absent in nearly all except the highest members 

 the class. Tonsils are generally met with ; and are largest in 

 the rapacious and carnivorous species. 



Soft palate. 



t A conical process prolonged from the middle of the pendulous margin of 

 the Soft-palate in Man, 



