AQUATIC MAMMALS 



that Phoca has a fuller complement of gustatory organs than any other 

 pinniped which he examined. 



The mouth of the hippopotamus is remarkable for its size. It has 

 evidently been developed thus partly by the stimulus of excessive use, 

 for it feeds upon succulent vegetation of very low nutritive value, and 

 hence must consume an enormous quantity. Indicative of this is the 

 fact that the stomach is upward of 15 feet in length, and even more 

 complicated than is usual in Artiodactyla. But the huge mouth is not 

 altogether an efficient apparatus, for mastication is a slow and laborious 

 process, and the animal has much difficulty in properly handling the 

 pendulous angles of the mouth. 



In the Cetacea the lips are always immobile, smooth and rubbery. In 

 Odontoceti the width and size of the mouth is never excessive, but is 

 quite variable, largely according to the size of the snout. Thus in Kogia 

 the very short mandible makes the mouth relatively very broad, while 

 in the long-snouted porpoises it is more beak-like. In the cachalot 

 (Physeter) the enormous mass of the head dwarfs the mouth by com- 

 parison, and yet the animal feeds upon the most bulky fare of any ceta- 

 cean. The tongue of the toothed whales is variable, but may be said 

 to be normal in function. It often has a fringe of papillae. Sonntag 

 (1922) said that "the tongues of the Cetacea have their glandular or- 

 gans better developed, but their gustatory and mobile functions are less, 

 than in other Mammalia." The tongues of Mysticeti agree with those 

 of Odontoceti in having filliform papillae scanty or absent, the mucosa 

 more or less corrugated, no trace of foramen caecum, lytta, frenal la- 

 mella, lateral organs, and apical gland of Nuhn. They differ as fol- 

 lows: 



Mysticeti Odontoceti 



tongue soft tongue firm and hard 



intermolar elevation present absent 



much oil in tongue absent 



apex massive not so 



marginal lobes absent present 



lateral borders ill-defined well-marked 



glands less numerous very numerous 



muscles slight or large well-developed 



mobility slight variable 



Salivary papillae and plicae fimbriatae are absent in both. In odonto- 

 cetes the surface of the tongue is rather parchment-like. It usually fills 



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