DIGESTION AND ABSORPTION OF NUTRIENTS 85 



alate 



tongue 



114. Structure and functions of the tongue. The tongue 

 is an elongated mass of muscle tissue (Fig. 27). The muscle 

 fibers run through it in three directions, and by their 

 separate or combined action the free end of this organ may 

 be moved about at 



will. When one ex- 

 amines the mucous 

 membrane on the 



upper surface of the /'fWfT^Ji^^^ = ^<^ \ ^ uvula 

 tongue, it is possible 

 to see elevations of 

 different sizes, called 

 papillae. Nerve fi- 

 bers carry messages 

 from these papillae 

 to the brain, and 

 thus we become 

 conscious of sen- 

 sations of taste. 

 Among the carniv- 

 ora or flesh-eating 

 animals the papillse 

 on the tongue are 

 especially rigid. This enables the dog, cat, lion, or tiger to 

 scrape the meat from the bones and to extract the marrow 

 after the bones are broken open. 



115. Study of the teeth. (Home work.) 



1. Bite off a piece of apple or bread. 



a. Describe the motion of the lower jaw in biting off a 



piece of food. 

 6. In what part of each jaw are found the teeth that are 



used in biting food ? 

 c. Describe the shape and cutting surface of these teeth. 



FIG. 27. Mouth cavity. 



