266 DIGESTION. 



is mixed in the mouth consist of the secretion of the 

 salivary glands, and the mucus secreted by the lining 

 membrane of the whole buccal cavity. 



The glands concerned in the production of saliva, are 

 very extensive, and in man and Mammalia generally, are 

 presented in the form of four 'pairs of large glands, the 

 parotid, submaxillary, sublingual, and numerous smaller 

 bodies, of similar structure and with separate ducts, which 

 are scattered thickly beneath the mucous membrane of the 

 lips, cheeks, soft palate, and root of the tongue. The 

 structure of all these glands is essentially the same. Each 

 is composed of several parts, called lobes, which are joined 

 together by areolar tissue ; and each of these lobes, again, 

 is made up of a number of smaller parts called lobules, 

 bound together as before by areolar tissue. Each of these 

 small divisions, called lobules, is a miniature representation 

 of the whole gland. It contains a small branch of the 

 duct, which, subdividing, ends in small vesicular pouches, 

 called acini) a group of which may be considered the 



dilated end of one of the smaller ducts (fig. 67). Each of 

 the acini is about -^-^ of an inch in diameter, and is formed 

 of a fine structureless membrane, lined on the inner surface 



* Fig. 67. Diagram of a racemose or saccular compound gland ; 

 m, entire gland, showing branched duct and lobular structure ; n, a lobule 

 detached, with 0, branch of duct proceeding from it (after Sharpey). 



