LESSON 61.] 



NUTRITION IN MAN. 



211 



917. During the time the molars are thus employed, the saliva 

 from the parotid glands is abundantly poured out from its ducts, 

 which open opposite to the second grinder, and in the meanwhile the 

 secretion from the other two pairs of salivary glands commingles 

 with the first, and thus the food becomes thoroughly insalivated, 

 whereby its living principle is destroyed, and incipient decomposition 

 induced. 



918. During this time the tongue is not idle its business is to 

 turn the food so that every surface of it may be presented to the mo- 

 lar teeth ; neither is this all, for the tongue conveys the food from 

 the molars on one side of the mouth to those on the other side, and 

 when this first and most important operation is completed, the 

 tongue conveys the food to the funnel-shaped cavity at the back of 

 the mouth, called the pharynx, from whence it is passed to the ceso- 

 phagus to be conveyed to the stomach. 



919. The tongue is used by man in suction ; the Canine and Fe- 

 line races employ the tongue to lap fluids ; the Giraffe twines this 

 organ around the leaves and branches of trees, and detaches them 

 with force. The Ant-eaters have a 



remarkably long tongue, covered 

 with a slimy secretion ; this they pro- 

 trude, and upon it entrap their vic- 

 tims. The Cameleon among reptiles, 

 and the Woodpecker among birds, 

 have each a tongue enormously de- 

 veloped, for the purpose of prehen- 



Fio. 884. 



sion. 



It has been already stated that 

 the human tongue, in common with 

 the like organ in other animals, pos- 

 sesses three distinct kinds of papillae ; 

 this will be best understood by con- 

 sulting the subjoined figure of the 

 human tongue (Fig. 334). The fili- 

 form papillae are seen at a, the fungi- 

 form at 2>, and the circumvallatae at 

 c. That the filiform papillae are en- 

 dowed with the sense of taste is cer- 

 tain, from the fact that the gustatory nerves (nerves of taste) are 

 extensively distributed to them; the precise function of the other 

 papillae is obscure. The white spots at the upper portion of the 



Human tongue. 



