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 resting acini are in the same secretory 

 condition, since quite usually certain cells have failed to participate 

 in the activity of their neighbors, and, in 

 consequence, appear as crescentic groups 

 of granular cells lying immediately next the 

 basement-membrane at the periphery of the 

 acinus, where they have been crowded by the 

 larger mucus-filled elements. These cres- 

 centic groups constitute the demilunes of 

 Heidenhain or the crescents of Gia- 

 nuzzi, and are aggregations of cells which 

 Section of human subiinguai h ave not participated in secretion. The ex- 



gland: among the clear cells 



lining the mucous acini are cretory tube ot the sublmgual gland, or the 

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



ments which constitute the _, - . . r ..,.,. 



demilunes of Heidenhain. nbro-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 



