THE SALIVARY GLANDS. 



697 



p ig . 268. Mucous gland: submaxillary of 



eight hours ' 



the later observers, however, the mucous cells do not actually dis- 



integrate, but form again new material during the period of rest, as in 



the case of the goblet cells of the intestine. In the mucous as in the 



albuminous cells observations upon pieces of the fresh gland seem 



to give more reliable results than those upon preserved specimens. 



Langley* has shown that in the fresh mucous cells of the submax- 



illary gland numerous large 'granules may be discovered, about 125 



to 250 to a cell. These 



granules are comparable to 



those found in the goblet 



cells, and may be inter- 



preted as consisting of mu- 



cin or some preparatory 



material from which mucin 



is formed. The granules 



are sensitive to reagents; 



addition of water causes 



them to swell up and dis- 



appear. It may be as- 



sumed that this happens 



during secretion, the gran- 



ules becoming converted to a mucin mass which is extruded from 



the cell. 



Action of Atropin, Pilocarpin, and Nicotin upon the Secre- 

 tory Nerves. The action of drugs upon the salivary glands and 

 their secretions belongs properly to pharmacology, but the effects 

 of the three drugs mentioned are so decided that they have a 

 peculiar physiological interest. Atropin in small doses injected 

 either into the blood or into the gland duct prevents the action of 

 the cerebral autonomic fibers (tympanic nerve or chorda tympani) 

 upon the glands. This effect may be explained by assuming that 

 the atropin paralyzes the endings of the cerebral fibers in the glands. 

 That it does not act directly upon the gland cells themselves seems 

 to be assured by the interesting fact that, with doses sufficient to 

 throw out entirely the secreting action of the cerebral fibers, the 

 sympathetic fibers are still effective when stimulated. Pilocarpin 

 has directly the opposite effect to atropin. In minimal doses it 

 sets up a continuous secretion of saliva, which may be explained upon 

 the supposition that it stimulates the endings of the secretory fibers 

 in the gland. Within certain limits these drugs antagonize each 

 other, that is, the effect of pilocarpin may be removed by the sub- 

 sequent application of atropin, and vice versa. Nicotin, according 

 to the experiments of Langley, f prevents the action of the secretory 



*" Journal of Physiology," 10, 433, 1889. 



f "Proceedings of the Royal Society," London, 46, 423, 1889. 



