Class 6. Mammalia. 487 



they form the cheeks and are absent only in rare cases. In some 

 Mammalia (e.g., many Apes, Rodents) there are cheek pouches 

 which serve as reservoirs for food. The tongue is very muscular, 

 strong, and movable, and is thus very useful in bringing food into 

 the mouth ; it is covered on its upper surface with small, pointed 

 processes [papiUce filiformes) which are sometimes much cornified 

 (in the Cat) ; there is also a small number of various other processes 

 [p. fungiformes, rirciimvallatre, and foliata), which bear taste buds.* 

 On the hard palate there is usually a double series of fairly hard 

 transverse folds, the palatal ridges, which often, e.g., in cattle, 

 project considerably ; or are almost or quite effaced (Man) ; for 

 the peculiar development of the palatine ridges in the Whale-bone 

 Whale, see Cetacea. Besides small glands embedded in the wall, 

 several large salivary glands open into the buccal cavity: 

 viz., the parotid, submaxillary, and sublingual. t 



The pharynx is continued into the CBSophagus which is 

 usually long and narrow. The stomach is generally a short, 

 wide, somewhat curved tube, provided, close to the entrance of the 

 oesophagus, with a short, blind sac which, however, passes quite 

 gradually into the general cavity. In some Mammalia the stomach 

 is compound, i.e., is divided by constrictions into several regions (in 

 certain Rodents, the Whales, Ruminants, etc.) : or it is characterised 

 by the possession of several short, blind sacs (in the pig) : or it differs 

 from the ordinary type in yet other ways, e.g., in being elongate 

 and intestine-like (Kangaroo). Usually it is entirely lined by a 

 cylindrical epithelium and its walls are furnished with numerous 

 glands (gastric and mucous) : sometimes, however, the epithelium 

 of the oesophagus, which is stratified like that of the mouth, reaches 

 some way into the stomach, and often it may e^xtend over a very 

 considerable area, in the Horse about half : in most Ruminants the 

 rumen, reticulum, and psalterium are lined with stratified epithelium. 

 The small intestine is of considerable length, longest in 

 herbivorous forms. That portion of the alimentary canal which 

 is designated rectum in Vertebrates, is generally of considerable 

 length in the Mammalia, usually fairly wide also, and is known as the 



* On each side of the ventral surface of the tongue, there is a fold which often 

 unites with that of the other side ; it is termed the " sub-lingua," and attains its 

 highest development in the Prosimii, where it forms a linguiform appendage of the 

 true tongue. In the anterior region of the tongue (Fig. 396) there is, close to the 

 lower side in many Mammalia, an elongate structure, the so-called worm {lysso,) ; it 

 is surrounded by loose connective tissue, and consists of muscular and connective 

 tissue ; sometimes it contains a cartilaginous portion, which apparently corresponds to 

 the anterior end of the hyoid of Lizards (Fig. 336). Behind, at the base of the tong-ue, 

 on each side, is the tonsil {ionsilla) (Fig. 396 t), a region of the mucous membrane 

 in which there are numerous lymph foUicles. Such follicles are also embedded in 

 other portions of the mucous membrane of the mouth, 



t The last, however, is not a single gland, but a group of small glands, each with 

 its duct. 



