MOUTH AND TONGUE 



6r 



be found at least traces of more cusps. Now in some of them 

 we may be dealing with instances of a complete tooth change ; 

 the suppression, save for one tooth, which is found in Marsupials, 

 was probably not developed in at least some of these early 

 mammals. The simplicity may therefore have been preceded 

 t>y complexity, and may have been merely an adaptation to an 

 insectivorous diet. 



Alimentary Canal. The mouth, of the Mammalia is remark- 

 able for the fact that with a few exceptions, such as the Whales, 

 there are thick and fleshy lips. The 

 office of these is to seize the food. 

 The roof of the mouth is formed by 

 the " hard palate " in front, which 

 covers over the maxillary and pala- 

 tine regions. This region is often 

 covered with raised ridges, which 

 have a symmetrical disposition, and 

 are particularly strong in Ruminant 

 animals. They are much reduced in 

 the Eodents, where the anterior part 

 of the palate is ill-defined owing to 

 the way in which its sides fade into 

 the lateral surface of the face. It 

 has been shown that these ridges, 

 in the Cat at least, develop as 

 separate papilliforrn outgrowths, and 

 it has been suggested that these 

 papillae, which later become united 

 to form the ridges, are the last remnant of palatine teeth such 

 as occur in lower vertebrates. 



The tongue is a well -developed organ, usually playing a 

 double part. It acts as an organ of prehension, especially in 

 such animals as the Giraffe and the Anteater, where it is 

 long and protrusible beyond the mouth for a considerable dis- 

 tance. It also carries gustatory organs, which serve for the 

 discrimination of the nature of the food. Beneath the tongue 

 there may be a hardish plate, known as the sublingua. This is 

 especially prominent in the Lemurs, where it projects as a horny 

 structure below the tongue, and has an independent and free tip. 

 It is supported in some of these animals by a cartilaginous 



FIG. 40. Palatal folds of the Raccoon 

 (Procyon lotor). p.p, Papilla pala- 

 tina ; r.p, palatal folds. (From 

 Wiedersheim's Structure of Max.) 



