NORMAL HISTOLOGY. 



lowing prolonged activity, the cells appear smaller, dark and 

 granular, and closely resemble the elements of the serous glands, 

 since the mucoid substance separating the particles of the cell pro- 

 toplasm has been removed, thereby allowing the displaced proto- 

 plasmic granules once more to approach closely. 



Not all the cells in the acini are of the same nature, since quite 

 usually small crescentic groups of granular cells lie immediately 

 next the basement-membrane at the pe- 

 FIG. 229. riphery of the acinus, where they have been 



crowded by the larger mucus - filled ele- 

 ments. These crescentic groups consti- 

 tute the demilunes of Heidenhain or 

 the crescents of Giannuzzi, which are 

 aggregations of cells belonging to the 

 serous type, similar to those of the parotid 

 acini. The submaxillary is, therefore, a 

 Section of human subiinguai mu co-serous or " mixed" gland. The ex- 



gland : among the clear cells 11-111 i 



lining the mucous acini are cretory tube of the subiinguai gland, or the 

 nests (g, g ) of granular eie- duct of Bartholin, consists principally of a 



ments which constitute the rl - . . ...,.,. 



demilunes of Heidenhain. fibro-elastic tunica propna, within which is a 



single layer of low columnar cells, while out- 

 side extends a supplementary layer of fibrous tissue. 



The submaxillary gland is a mixed gland, certain lobules being 

 composed of acini of the serous type, while neighboring divisions 

 contain those of the mucous variety. 



The excretory channel, or the duct of Wharton, resembles that 

 of the parotid gland, dividing into the smaller tubes lined by striated 

 "rod" epithelium, passing thence into the intermediate tubules, with 

 low cuboidal cells, which lead into the serous acini filled with dark 

 granular cells on the one hand, or into those filled with mucous cells 

 and granular crescents on the other. 



The vascular supply of the salivary glands is very rich ; while 

 the arrangement of the blood-vessels in the several glands presents 

 unimportant differences, their distribution is according to the same 

 general plan. 



The larger arteries accompany the excretory ducts of the glands 

 within the interlobular fibrous septa, where they give off branches 

 which pass between the lobules and later penetrate the tissue of the 

 lobules to end in rich capillary net-works enclosing the acini. The 

 capillaries lie immediately outside the basement-membrane in prox- 

 imity to the secreting cells. The veins follow the general course 

 taken by the arteries. 



The lymphatics are represented by indefinite interfascicular clefts 

 between the acini, which are taken up by definite lymph-vessels 



