DIGESTION OF FOOD: THE MOUTH 



Nerve 



' Vein 



Artery 



FIG. 41. DIAGRAM 



Showing the positions of the 

 parotid and submaxillary 

 glands. 



even the thought of it produces the same effect a watery 

 liquid, the saliva, begins to be poured into the mouth. 

 This comes from three pairs of 

 salivary glands. 1. The parotid, 

 j ust below and in front of each ear, 

 with long ducts opening through the 

 sides of the mouth opposite the 

 second molar teeth. 2. The sub- 

 lingual, beneath the tongue, with 

 numerous separate ducts. 3. The 

 submaxillary, beneath the tongue, 

 on each side, near the angle of the 

 jaw; Fig. 41. The ducts of these 

 last open under the tongue, on each 

 side of the middle, toward the front, 

 on slight elevations. 



These salivary glands are com- 

 pact masses of varying sizes. The 



parotids are flat and of almost the same area as the ear; 

 the submaxillaries are about the size of. a walnut. Under a 

 microscope they are found to consist of many minute cavities. 

 If one imagines a cluster of extremely small grapes, which are 

 hollow, and discharge sap into their stems, he will get a good 

 picture of the structure of such a gland; Fig. 42. Each spher- 

 ical cavity (or each grape in the illustration) is called an 

 alveolus, and each has its walls made of cells. The cells 

 extract from the blood material out of which they make 

 saliva; this they pour into a little duct which drains the 

 alveolus. Each duct joins others from other alveoli, and all 

 finally unite to form a single duct which carries the secretion 

 into the mouth. These little clusters of hollow sacs are micro- 

 scopic, very numerous, and all bound together into a compact 

 mass. Several other glands in the body are constructed on 

 the same plan, and this pattern is called racemose from a 

 Latin word that means " full of clusters." 



