264 



COMPARATIVE ZOOLOGY 



monotremes lips are wanting, and in the porpoises they 

 are barely represented. But in the herbivorous quadru- 

 peds they, with the tongue, are the chief organs of pre- 

 hension ; in the carnivorous tribes they are thin and 

 retractile ; while in the whale the upper lip falls down 

 like a curtain, overlapping the lower jaw several feet. 

 As a rule, the mouth is terminal ; but in the elephant, 

 tapir, hog, and shrew, the upper 

 lip blends with the nose to 

 form a proboscis, or snout. The 

 mouth is comparatively small in 

 the elephant and in gnawing 

 animals like the squirrel, wide 

 in the carnivores, short in the 

 sloth, and long in the ant-eater. 

 Teeth are usually present, but 

 vary in form and number with 

 the habits of the animal. The 

 ant-eater is toothless, and the 

 Greenland whale has a sieve 



FIG. 225. Human Tongue and ad- made of homy platCS. The 

 jacent parts: a, lingual papillae; 



b, papiiise forming V-shaped tongue conforms in size and 



lines; d, fungiform papillae; e, , ., ,-, -, . j 



filiform papillae; g , epiglottis; shape with the lower jaw, and 



-., uvula or conical process, '^ a muscu l ar sensitive Organ, 



hanging from the soft palate, 



n; o, hard palate; r, palatine which SCrVCS many 



glands, the mucous membrane . 



being removed; v, section of the assisting in the prehension, 



tication, arid swallowing of food, 



besides being an organ of taste, touch, and speech. Its 

 surface is covered with minute prominences, called 

 papilla, which are arranged in lines with mathematical 

 precision. In the cats, these are developed into recurved 

 spines, which the animal uses in cleaning bones and 

 combing its fur. Similar papillae occur on the roof and 

 sides of the mouth of the ox and other ruminants. In 

 some animals, as the hamster and gopher, the cheeks 



