THE SUBxMAXILLARY GLAND 



237 



APPENDIX III 



THE SUBMAXILLARY GLAND— AN INSTANCE OF 

 ORGANIC FUNCTIONING 



Three pairs of glands open into the mouths of mammalian 

 animals: the sublingual, submaxillary, and parotid salivary 

 glands. Their function is to secrete saliva. Saliva consists 

 mostly of water which contains some mineral salts, some soluble 

 proteids, some mucin, and, in some animals, an enzyme called 

 ptyalin, which has the power of dissolving starch and converting 

 the latter into sugar. Saliva mixes with the food, so that the 

 latter can be worked up into a " bolus," which is then swallowed; 

 it cleans the mouth in that it removes dirt in the " spittle," and 

 it may be a digestive ferment, or enzyme. 



Fig. 52. — A Diagram of a Salivary Gland with its Vessels, 

 Nebves, and Duct. 



The gland itself consists of a very great number of alveoli 

 which are connected with ductules, which unite to form the duct 

 which opens into the mouth. The saliva is formed, or secreted, 

 in the cells which constitute the walls of the alveoli. Leaving 

 the details for a moment, note the structures connected with the 

 gland. 



An artery conveys blood to it. The latter circulates round 

 the alveoli, and leaves the gland by means of a vein. Lymphatic 

 vessels are also connected, and through these a watery fluid, 

 called lymph, leaves the gland and finally enters the circulating 

 blood of the body. 



A duct leaves the gland, and through this the saliva that is 

 secreted in the alveoli reaches the mouth. 



