OF THE TONGUES OF THE MAMMALIA. 281 



Owen (13) considers that the first part of the stomach replaces 

 the cheek-pouches. I believe his opinion to be correct and 

 would add that the leaves, mixed with the copious secretions of 

 the lingual and salivary glands, lie in the first part of the stomach 

 till insalivation is completed. 



The Anthropoid Apes have no cheek-pouches, a very high 

 development of the basal lingual glands, and a simple stomach. 

 They eat fruits and shoots which are more succulent than the 

 food of the Langurs, and a complex digestive apparatus is not 

 so necessary. 



The Cercopitheques, Macaques, Baboons and Mangabeys 

 have cheek-poaches, a moderate degree of development of lingual 

 and salivary glands, and a simple stomach. They live on a 

 succulent diet and store food in their cheek-pouches. A little 

 food can be removed from time to time, insalivated thoroughly 

 and swallowed. I would suggest that cheek-pouches are, conse- 

 quently, part of the digestive apparatus, and not only store- 

 houses. 



In the Ungulata the process of rumination obviates the 

 necessity for largely-developed lingual glands. 



The Three-toed Sloth {Bradypus tridactylus) resembles the 

 Langurs in the nature of its diet, but the physiology of 

 the tongue and stomach is different. The tongue is mainly 

 mechanical in function, for its gustatory and secretory organs are 

 small. Pi-ehension is its strongest mechanical action. As the 

 stomach contains many hard, almost entire leaves, mastication 

 and insalivation cannot be very complete. Moreover, there are 

 no cheek-pouches to prolong the stay of the food in the buccal 

 area. Consequently, the stomach must soften the leaves for it 

 gets little assistance from the tongue and salivary glands. It 

 also cannot share the process of digestion with the caecum. The 

 ruminating gutter running through the stomach takes on the 

 regurgitant function of the oesophagus of the Ruminantia. 



In the Koala (Phascolarctos cinereus) there are large cheek- 

 pouches, the lingual glands are well-marked, and the salivary 

 glands, especially the parotids, are large. The stomach is simple 

 and the caecum enormous. The leaves remain long in the buccal 

 area, in virtue of the cheek-pouches, and can be thoroughly 

 moistened and softened. They then pass to the stomach, but the 

 effect of the peculiar gastric gland has not been worked out. 

 The stomach, however, does not play such an important part as 

 in the Langurs and Sloths, for much of its work is taken away 

 by the enormous caecum. 



These remarks indicate that the cheek-pouches are not entirely 

 storehouses, and show how the functions of the different parts are 

 interdependent. They also demonstrate how a diet of leaves 

 requires a complex stomach and small caecum, or a simple stomach 

 and a large complex caecum, for its digestion. 



