180 



THE INTERNAL ENVIRONMENT OF THE BODY 



PHY 



Part III 



PAROTID 

 SALrVARY GLANO 



OUCT OF PAROTID GLANO 

 OPEN'NG INTO MOUTH 



SUBMAXILLARY 

 SALIVARY GLANO 



3 6L 



SUBLINGUAL 

 SALIVARY GLANO 



Fig. 11.8. Salivary glands. Left, In man the salivary glands are under the con- 

 trol of the autonomic (involuntary) nervous system. The parotid unit is stimu- 

 lated indirectly by dry food and by acids. Substances in solution stimulate the 

 taste buds of the tongue, nervous impulses are sent to salivary centers in the 

 hind part of the brain, and are relayed by nerves to the salivary glands. Right, 

 In the honeybee the salivary glands are relatively enormous. There are two pairs 

 packed between the air sacs in the head and around pharynx (PHY) and the 

 brain (pharyngeal and cephalic) (IGL, 2GL), and another pair (thoracic) (3GL) 

 extends into the thorax and about the esophagus (OE). In bees the uses of saliva 

 are highly social: in royal jelly food for the young queen; mixed with honey; 

 mixed with the wax for the comb, and other materials. {Left, Courtesy, Mac- 

 Dougall and Hegner: Biology. New York, McGraw-Hill Book Co., 1943. Right, 

 Courtesy, Snodgrass: U. S. Bureau Entomology Technical Series Bull. No. 18.) 



Carnivorous teeth 

 Dog 



Herbivorous teeth 

 Cow 



Fig. 11.9. Carnivorous teeth of a dog and herbivorous teeth of a cow. Car- 

 nivores have few cheek teeth and those shear like scissors. Dogs grip their food 

 with their stabbing upper canines and gulp it hurriedly. Herbivorous mammals 

 have full sets of cheek teeth with high crowns resistant to grinding. Cattle have 

 no canines and no upper incisors but clinch grass between their lower incisors and 

 a horny pad on the upper jaw. 



