IO6 SALIVARY GLANDS. 



the alimentary canal farther on is out of order, the 

 tongue is apt to be covered with a thick yellowish coat- 

 ing, and there is a "bad taste" in the mouth. This may 

 in most cases be taken as a sign that there is something 

 wrong with the stomach. 



15. The Salivary Glands. The liquid which moistens 

 the mouth is named saliva. It consists of a slimy fluid, 

 named mucus, made, or secreted, as we say in physiology, 

 by the tiny glands of the mucous membrane, mixed 

 with a more watery secretion made by three pairs of 

 salivary glands. These glands lie outside the mouth, but 

 pour their secretion into it through tubes or ducts. Two 

 of the salivary glands are placed in front of the ears ; 

 their ducts open on the inside of the cheek opposite 

 the second upper molar tooth. In the disease known 

 as mumps they become greatly swollen. The other sali- 

 vary glands lie between the halves of the lower jaw- 

 bone. Their ducts open into the mouth beneath the 

 tongue. 



16. The Uses of Saliva are several, (i) It keeps the 

 mouth moist and enables us to speak with comfort. 

 This is well illustrated by the trouble from dryness of 

 the mouth experienced by many young orators when 

 they first try to speak in public. The dryness is due 

 to the fact that nervous excitement for a time para- 

 lyzes the salivary glands and stops their secretion. (2) 

 The saliva enables us to swallow dry food. A cracker 

 when chewed would give rise merely to a heap of dust, 



15. What is saliva? How made? Describe the position of the 

 salivary glands. Where do the ducts of each pair open ? 



16. What is the first use of saliva? Illustrate. The second? 

 Illustrate. The third? Illustrate. The fourth? 



