72 THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



serous glands which open into the mouth cavity. The chief 

 salivary glands are three in number on each side of the 

 mouth the parotid, submaxillary and sublingual. Besides 

 these, there are, throughout the buccal mucous membrane, a 

 number of smaller glands of similar structure contributing 

 to the formation of saliva. The parotid gland is situated 

 just beneath and in front of the lobe of the ear; the sub- 

 maxillary beneath the mandible about the center of the base 

 of the submaxillary triangle, and the sublingual beneath the 

 mucous membrane of the mouth, just lateral to the lingual 

 frenum. 



F IG- 33. Cells of the alveoli of a serous or watery salivary gland. 

 (Brubaker after Yeo.} 



A, after rest; B, after a short period of activity; C, after a prolonged period 

 of activity. 



The duct from the parotid, Stenson's duct, runs beneath 

 the mucous membrane of the cheek to a point opposite the 

 second upper molar tooth, where is its opening into the 

 mouth. The duct from the submaxillary, Wharton's duct, 

 discharges the secretion from that gland into the mouth by 

 the side of the frenum of the tongue. The secretion from 

 the sublingual reaches the mouth by a. number of small ducts 

 (Rivinus) which open also by the side of the frenum, and 

 sometimes as well by a larger duct, Bartholin's, which runs 

 parallel with Wharton's and empties near it. 



Histology. In structure the salivary glands have been 

 shown to be of the compound tubular variety, the secreting 

 part being tubular. The parotid is a serous gland, the other 



