THE DIGESTIVE APPARATUS AND NUTRITION 219 



Next to them come the canines, one on each side, then the 

 two bicuspids, or premolars, and next to them three molars 

 on each side. The third pair of molars on each jaw are 

 called the wisdom teeth, and they sometimes fail to appear. 



Opening of 

 Kustachiantube 



Soft palate 



Epiglottis 



Glottis 

 Esophagus 



Larynx 



~~ Hard palate 



Tongue 



Hyoid bone 



False vocal cords 



True vocal cords 



Thyroid carti- 

 lage 



--"--==, Cricoid carti- 

 lage 



Fig. 108. Vertical section of the head and neck. 



The teeth of different animals are adapted 'in form and 

 structure to the food upon which they subsist. Carnivo- 

 rous animals are provided with strong, sharp teeth for 

 seizing and tearing flesh, while the teeth of herbivorous 

 animals are broader and relatively shorter, with wide- 

 ridged surfaces for grinding grains and plant fiber. Man, 

 as requiring both animal and vegetable food, is provided 

 with teeth of both sorts. 



309. Structure of a Tooth (Fig. 109). A tooth has three 

 parts, crown, neck, androote. The crown is the part which 

 projects beyond the gum, and is covered with the firm, 



