476 



SALIVA 



[CH. XXX. 



more fully in connection with the gastric glands and the pancreas 

 where they have been separated from the ferments by chemical methods. 

 In the case of saliva we may term the zymogen, ptyalinogen provision- 

 ally, but it has never been satisfactorily separated chemically from 

 ptyalin. 



After secretion, due to the administration of food or of such a 

 drug as pilocarpine, the cells shrink, they stain more readily, their 



Fia. 306. Alveoli of parotid gland. A, before secretion ; B, in the first stage of secretion ; C, after 

 prolonged secretion. (Langley.) 



nuclei become more conspicuous, and the outer part of each cell becomes 

 clear and free from granules (fig. 396). 



The Secretory Nerves of Salivary Glands. 



The nerve-fibres which are derived from cranial and sympathetic 

 nerves ramify between the gland-cells, but have never actually been 

 traced into them. 



These nerves control and regulate the secretion of saliva. 



The general truth concerning the existence of secretory nerves, we 

 have already become acquainted with (p. 162). The subject has been 

 worked out most thoroughly in connection with the salivary glands, 

 particularly the submaxillary gland of the dog, which we will 

 take first. 



The Submaxillary and Sublingual Glands. These glands 

 receive two sets of nervet-fibres; namely, from the chordi tympani 

 and the sympathetic. *^v? 



The chorda tympani is given off from the seventh cranial nerve in 

 the region of the tympanum.* After quitting the temporal bone it 

 passes downwards and forwards, and joins the lingual nerve, with 

 which it is bound up for a short distance. On leaving the lingual 

 nerve it traverses the sulmaxillary ganglion ; it then runs parallel to 

 the duct of the gland, gives off a branch to the sublingual gland, and 



* Though the chorda tympani is usually spoken of as a branch of the seventh 

 nerve, it is probable that some of its sensory fibres are derived from the glosso- 

 pharyngeal ; the origin of its secretory fibres is not known. 



