THE NERVES OF THE SALIVARY GLANDS. 



211 



in mucin, small microscopic pieces of mucin are found, and sometimes mucous cells themselves 

 are present. Or, we must assume that the mucous cells simply eliminate the mucin from their 

 bodies (Ewald, Stohr) ; while, after a period of rest, new mucin is formed. According to this 

 view, the dark granular cells of the glands, after active secretion, are simply mucous cells, which 

 have given out their mucin. If we assume, with Heidenhain, that the mucous cells break up, then 

 these granular non-mucous cells must be regarded as new formations produced by the prolifera- 

 tion and growth of the composite marginal cells, i.e., the crescents, or half-moons of Gianuzzi. 



[During rest, the protoplasm seems to manufacture mucigen, which is changed 

 into and discharged as mucin in the secretion, when the gland is actively secreting. 

 Thus, the cells become smaller, but the protoplasm of the cell seems to increase, 

 new mucigen is manufactured during rest, and the cycle is repeated.] 



144. THE NERVES OF THE SALIVARY GLANDS. The nerves are for the 

 most part medullated, and enter at the hilum of the gland, where they form a 

 rich plexus provided with ganglia between the lobules. [There are no ganglia in 

 the parotid gland (Klein). ~\ 



All the salivary glands are supplied by branches from two different nerves from 

 the sympathetic and from a cranial nerve. 



1. The sympathetic nerve gives branches (a) to the sub-maxillary and the sub- 

 lingual glands, derived from the plexus on the external maxillary artery ; (b) to the 

 parotid gland from the carotid plexus -{fig. 159). 



Scheme of the nerves of the salivary glands. P., pons ; M.O., medulla oblongata ; J.N., nerve of 



Jacobson ; 0., S.M., I.M., ophthalmic, superior, and inferior maxillary divisions of fifth 



nerve, V.; VII., seventh nerve; S.s.p., small superficial petrosal nerve; Vag., vagus; 



Sym., sympathetic ; O.G., otic, and S.G., submaxillary ganglia ; P., S., and S.L., parotid, 



submaxillary, and sublingual glands ; T. , tongue. 



2. The facial nerve gives branches to the sub-maxillary and sub-lingual glands from 



the chorda tympani, which accompanies the lingual branch of the fifth nerve (fig. 159). 



The branches to the parotid arise from the tympanic branch of the glosso-pharyngeal 



nerve (dog). The tympanic plexus sends fibres to the small superficial petrosal 



nerve, and with it these fibres run to the anterior surface of the pyramid in the 



temporal bone, emerging from the skull through a fissure between the petrous and 



great wing of the sphenoid, and then joining the otic ganglion. This ganglion 



sends branches to the auriculo-temporal nerve (itself derived from the third branch 



of the trigeminus), which, as it passes upwards to the temporal region under cover 



of the parotid, gives branches to this gland. 



The sub-maxillary ganglion, which gives branches to the sub-maxillary and sub- 

 lingual glands, receives fibres from the tympanico-lingual nerve (chorda tympani) 

 as well as sympathetic fibres from the plexus on the external maxillary artery. 



Termination of the Nerve-Fibres. With regard to the ultimate distribution of 

 these nerves we can distinguish (1) the vaso-motor nerves, which give branches to 

 the walls of the blood-vessels, and (2) the secretory nerves proper. 



