INSALIVATION. 177 



ganglion, and finally the auriculotemporal branch of the inferior 

 maxillary division of the fifth nerve or trigeminus. This is 

 shown in Fig. 101. (2) The cervical sympathetic, which is dis- 

 tributed principally to the walls of the blood-vessels, although 

 some of its fibers, in some animals at least, are secretory. 



The nervous supply of the submaxillary and sublingual glands, 

 like that of the parotid, is also double, the chorda tympani, a 

 branch of the seventh or facial, and branches of the sympathetic 

 plexus around the facial artery, being the nerves supplying 

 these glands. There is excellent authority for the statement 

 that the chorda tympani is in reality a branch of the glos- 

 sopharyngeal which joins the facial in the tympanum. The 

 chorda tympani joins the lingual nerve for a part of its course, 

 and then leaves it to pass through the so-called submaxillary 

 ganglion to the glands. It has been suggested that this would be 

 more properly called the sublingual ganglion, inasmuch as only 

 those fibers which are distributed to the sublingual gland are in 

 communication with the nerve-cells of this ganglion, while those 

 which pass to the submaxillary gland connect with a collection of 

 nerve-cells in that gland, Langley's ganglion. The course of the 

 chorda tympani is shown in Fig. 102. 



Effect of Stimulation of the Chorda Tympani and Sympathetic 

 Nerves. If the chorda tympani of a dog is stimulated by passing 

 through it weak induction shocks, the submaxillary gland secretes 

 more saliva. The small arteries of the gland are dilated and a 

 larger amount of blood passes through the gland, giving it a dis- 

 tinctly reddish appearance. Stimulation of the sympathetic fibers 

 produces a diminution in the secretion, and the reddish color dis- 

 appears, leaving the gland pale, a change evidently due to a con- 

 striction of the blood-vessels. It might at first seem that the 

 increase in the amount of blood caused by the stimulation of the 

 chorda tympani would explain the increased secretion of saliva by 

 filtration of the fluid of the blood through the vessel-walls, but 

 experiments have shown that there are in this nerve true secretory 

 fibers i. e., fibers which carry impulses to the secretory structure 

 of the gland, and that the cells are directly stimulated to increased 

 action. We may briefly refer to three of these experiments: 1. 

 If the blood-supply of the gland is cut off, and the chorda tym- 

 pani stimulated, the secretion of saliva will still be increased. 

 2. If atropin is injected into the animal and the chorda tympani 

 then stimulated, the blood-vessels will be dilated, but there will 

 be no secretion. 3. If hydrochlorate of quinin is injected into 

 the gland, the blood-vessels dilate, but no secretion follows. It 

 will be seen from these experiments that two effects are produced 

 by stimulation of the chorda tympani : 1. A dilatation of the 

 blood-vessels; and 2. A direct stimulation of the cells. From 

 this it is evident that there are two sets of fibers in this nerve, 



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