DIGESTION. 



65 



The submaxillary is supplied by the chorda tympani, which contains 

 two kinds of fibers: the secretory and the vasodilator. If you give 

 atropine you can paralyze the endings of the secretory fibers while 

 the vasodilators still continue their activity. Injection of sodium 

 bicarbonate into the duct of Wharton arrests the action of the 

 secretory fibers and leaves intact the vasodilators. Pilocarpine and 

 muscarine increase the flow of saliva by stimulating the endings 

 of the chorda tympani anci will remove the paralysis caused by 

 atropine. Opium makes the mouth dry by acting on the center of 

 salivation. The salivation by mercury is due to excessive metabo- 



D 



Fig. 12. Parotid of a Rabbit in Fresh State. (LANGLEY.) (From 

 Tigerstedt's "Human Physiology," copyright, 1900, by D. Appleton and 

 Company. ) 



A, Resting gland. B, Gland after a small dose of pilocarpin. C, Irritation 

 of cervical sympathetic. D, After strong irritation of cervical sympathetic. 



lism of the gland-cells themselves. When the chorda is stimulated 

 by electricity, the pressure* in the excretory duct is greater than 

 the blood-pressure of the animal. During this stimulation the tem- 

 perature is elevated. When the chorda tympani is stimulated the 

 blood-vessels of the gland dilate and the veins are red and pulsate 

 because the arterial blood rushes rapidly through them. The 

 antagonistic nerve which slows the secretion of saliva, both in the 

 submaxillary and parotid gland, is the cervical sympathetic. At 

 the same time, owing to its vasoconstrictors, the blood-vessels are 

 contracted. Hence in the submaxillary we have as a secretory nerve 



5 



