SALIVARY GLANDS 75 



constrictor. The secretory and vaso-dilator reach the gland 

 in the cerebro-spinal trunks ; the vaso-constrictor in the sym- 

 pathetic. The vaso-constrictors and vaso-dilators are dis- 

 tributed to the walls of the blood vessels, and influence secre- 

 tion indirectly only by increasing or diminishing the amount 

 of blood going to the glands. The secretory fibers exert their 

 influence directly upon the gland cells. It is claimed also 

 that the secretory fibers are divided into sets controlling the 

 production of the energy-yielding constituents and sets con- 

 trolling the production of water and salts. 



The parotid gland receives its cerebro-spinal fibers through 

 a branch of the fifth nerve, but when they are traced back- 

 ward it can be shown that they are in the tympanic branch 

 of the ninth, and pass from this branch to the small super- 

 ficial petrosal nerve and thence to the optic ganglion from 

 which ganglion they run to the parotid gland by the way of 

 the auricula-temporal branch of the third division of the 

 fifth. The cervical sympathetic also sends fibers to this gland. 



The submaxillary and sublingual glands are supplied by 

 the same nerves. Their cerebro-spinal fibers leave the brain 

 by way of the facial, follow the chorda tympani as far as a 

 short distance beyond its junction with the lingual nerve, 

 and then leave it to reach the submaxillary ganglion and 

 run thence to the submaxillary and sublingual glands. These 

 glands receive sympathetic fibers from the superior cervical 

 ganglion. 



Influence of Nerve Supply. Taking the parotid as an ex- 

 ample, it is found that stimulation of its cerebro-spinal fibers 

 produces an abundant watery flow of saliva ; the gland be- 

 comes decidedly redder, pulsation is sometimes apparent, 

 and it is evident that the amount of blood is locally increased. 

 When the sympathetic supply of the parotid is stimulated, the 

 secretion is inhibited or reduced to a minimum, the gland be- 

 comes pale and the amount of blood in it is evidently dimin- 

 ished. 



Similar corresponding results are occasioned in the sub- 



