160 TEXT-BOOK OF PHYSIOLOGY. 



ous coloring-matters. These are known as the demilunes of Heiden- 

 hain. At one time it was supposed that they were young cells des- 

 tined to take the place of the clear cells which were believed to be 

 exhausted and to have undergone disintegration. At the present time 

 they are regarded as albuminous or serous cells which exhibit changes 

 similar to the cells of the parotid gland. 



The glands embedded in the mucous membrane covering the 

 tongue, lips, cheek, palate, and pharynx are for the most part lined 

 with epithelial cells which contain a highly refracting matter similar 

 to, if not identical with, that found in the cells of the submaxillary 

 and sublingual glands. 



Nerve-supply. Experimental research has demonstrated that 

 each salivary gland receives nerve-fibers which influence the pro- 

 duction of the secretion ("secretory nerves) and fibers which dilate or 

 constrict the blood-vessels (vaso-dilator and vaso-constrictor nerves). 



FIG. 63. SECTION OF HUMAN PARO FIG. 64. SECTION OF HUMAN SUB- 



TID GLAND INCLUDING SEVERAL LINGUAL GLAND. Among the 



ACINI, d. Cut intralobular duct. clear cells lining the mucous 



(Piersol.} acini are nests (g, g} of granular 



elements which constitute the 

 demilunes of Heidenhain. 



The secretory fibers penetrate the basement membrane and finally 

 terminate between and on the surface of the secretory cells. The 

 vaso-motor fibers terminate between and on the muscle-cells in the 

 walls of the blood-vessels. The nerve-fibers in direct relation with 

 the cells and blood-vessels of the parotid gland are derived from the 

 otic ganglion. The cells of this ganglion are, however, invested by 

 the terminal branches of other nerve-fibers (preganglionic) derived 

 from the medulla oblongata. The relation of these preganglionic 

 fibers to the blood-vessels and cells is shown by the increase in 

 secretion and a change in the caliber of the vessels when they are 

 subjected to electric stimulation. The nerve-fibers which are in 

 direct relation with the vessels and cells of the submaxillary and 

 sublingual glands are derived from the submaxillary, the sublingual, 

 and the superior cervical ganglia. These local ganglion cells are 

 also closely invested by the terminal branches or arborizations of the 



