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PHYSIOLOGY OF DIGESTION AND SECRETION. 



pass close to this ganglion, but Langley has shown that only those 

 destined for the sublingual gland really connect with the nerve 

 cells of the ganglion, and he suggests, therefore, that it should 

 be called the sublingual instead of the submaxillary ganglion. The 

 nerve fibers for the submaxillary gland make connections with nerve 

 cells lying mainly within the hilus of the gland itself. The supply 

 of sympathetic autonomies has the same general course as those 

 for the parotid, namely, through the cervical sympathetic to the 

 superior cervical ganglion and thence to the glands. 



Histological Structure. The salivary glands belong to the type 

 of compound tubular glands. That is, the secreting portions are 

 tubular in shape, although in cross-sections these tubes may pre- 

 sent various outlines according as the plane of the section passes 

 through them. The parotid is described usually as a typical serous 

 or albuminous gland. Its secreting epithelium is composed of cells 

 which in the fresh condition as well as in preserved specimens contain 

 numerous fine granules and its secretion contains some albumin. 

 The submaxillary gland differs in histology in different animals. 

 In some, as the dog or cat, the secretory tubes are composed chiefly 

 or exclusively of epithelial cells of the mucous type. In man the 

 gland is of a mixed type, the secretory tubes containing both mucous 

 and albuminous cells. The sublingual gland in man also contains 

 both varieties of cells, although the mucous cells predominate. In 

 accordance with these histological characteristics it is found that the 

 secretion from the submaxillary and sublingual glands is thick and 

 mucilaginous as compared with that from the parotid. 



The salivary glands possess definite secretory nerves which when 

 stimulated cause the formation of a secretion. This fact indicates 

 that there must be a direct contact of some kind between the gland 

 cells and the terminations of the secretory fibers. The ending of the 

 nerve fibers in the submaxillary and sublingual glands has been de- 

 scribed by a number of observers. * The accounts differ somewhat as 

 to details of the finer anatomy, but it seems to be clearly established 

 that the secretory fibers from the chorda tympani end first around the 

 intrinsic nerve ganglion cells of the glands (preganglionic fibers), and 

 from these latter cells axons (postganglionic fibers) are distributed 

 to the secreting cells, passing to these cells along the ducts. The 

 nerve fibers terminate in a plexus upon the membrana propria of the 

 alveoli, and from this plexus fine fibrils pass inward to end on and 

 between the secreting cells. It would seem from these observations 

 that the nerve fibrils do not penetrate or fuse with the gland cells, 

 as was formerly supposed, but form a terminal network in contact 

 with the cells, following thus the general schema for the connection 

 between nerve fibers and peripheral tissues. 



* See Huber, "Journal of Experimental Medicine," 1, 281, 1896. 



