30 SECRETION. 



confirmed and extended by the subsequent observations of 

 Bernard and other physiologists. The following are the 

 most important facts, taken from Bernard, bearing upon the 

 question under consideration : l 



" Introducing into the mouth of a dog, in which the three 

 salivary ducts have been isolated, a very sapid substance, 

 such as vinegar, for example, it is found that the duct of the 

 submaxillary discharges saliva in very great abundance. 

 But, by operating directly upon the nerve of taste itself, I 

 have been enabled to act solely upon the special secretion, 

 and to demonstrate directly this intimate relation between 

 the secretion of the submaxillary saliva and the sense of gus- 

 tation. 



" When we divide in a dog the lingual nerve opposite the 

 middle of the horizontal process of the lower jaw, and pinch 

 the central end, which is connected with the encephalon, we 

 immediately see the duct of the submaxillary excrete saliva 

 with great activity, while the ducts of the parotid and sub- 

 lingual, which are not connected with the sense of gustation, 

 remain perfectly dry. This sort of functional reaction, which 

 irritation of the central end determines exclusively, in the 

 submaxillary gland, is explained, for in operating thus we 

 produce in the nervous centre the impression of exaggerated 

 gustatory sensation, which immediately provokes, by an ac- 

 tion called reflex ! , the salivary secretion destined physiologi- 

 cally to allay and diminish the too acute impression of sapid 

 substances." 



These experiments clearly demonstrated the importance 

 of the nervous influence in the production of the secretions ; 

 but the more recent observations of Bernard show that the 

 effects are produced mainly by increasing the activity of the 

 circulation in the glands. This takes place in greatest part 

 through filaments from the sympathetic system, which are 



1 BERNARD, Recherches cTanatomie et de physiologie comparee sur ies ylandes soli- 

 vaircs chez Thomme et Ies animaux vertebres. Comptes rendus, Paris, 1852, tome 

 xxxiv., p. 239. 



