390 



THE DIGESTIVE SYSTEM 



the discharge of the mucus during secretion, is presumably capable of 

 reloading the cell with its mutinous content. 



We will now consider the more important peculiarities of each of 

 the larger salivary glands. 



The Parotid Gland. This is the largest of the salivary glands and 

 in man, sheep, dog, cat and rabbit is purely a serum-secreting organ. 

 However, in sheep, dog and cat it contains also a variable number of 



mucous alveoli during 

 the first year; these de- 

 generate and entirely 

 disappear during the 

 second year (Brock and 

 Trautmann, Anat. An/,., 

 47, 17, 1914). 



It is situated in 

 front of the external 

 ear, and overlaps in- 

 feriorly both faces of 

 the upper portion of the 

 ramus of the mandible. 

 A variable number of 

 small accessory lobules, 

 including mucus-pro- 

 ducing alveoli, lie along 

 the course of the main 

 parotid ( Stenson's) 

 duct. The latter opens into the mouth at the level of the second upper 

 molar. The parotid is invested by a dense fibre-elastic sheath, septa from 

 which divide the gland into lobes and lobules. The lobes and lobules are 

 firmly united by the dense but narrow bands of connective tissue ; these 

 contain the larger ducts, blood-vessels, lymphatics, and a few small gan- 

 glia. 



The secreting acini are relatively long and tortuous; they are fre- 

 quently branched or forked. Because of the relatively low height of 

 their serum-secreting cells the acini appear slender and their lumen is 

 irregular, indistinct, and very narrow. The 'basket cells' upon which the 

 secreting cells rest are highly developed in the parotid and often form 

 a complete investment for the acinus. 



The acini of the parotid are all of one type. The only other tubules 

 within the lobules of this gland.are the intercalary and the iutralobular 



FIG. 361. FROM A SECTION OF THE HUMAN PAROTID 



GLAND. 



I, lumen of a serous acinus; sch, intercalary duct; 

 sr, intralobular duct; T, secreting acini. Hematoxy- 

 lin and eosin. X 280. (After Sobotta.) 



