Sfecr. XXiV. 2. OF THE SALIVA AND TEARS. 315 



7. A preternatural flow of faliva is likevvife foiae- 

 times occaiioncd by a difeafe of the voluntary power ; 

 for if xve think about our faliva> and determine not 

 to (wallow it, or not to fpit it out, an exertion is 

 produced by the will, and more faliva is fecreted 

 againft our wifll ; that is, by our averfion, which 

 bears the fame analogy to defire, as pain does to 4 

 pleafure ; as they are only modifications of the fame 

 difpofitioh of the fenforium. See Clafs IV. 3. 2. i. 



8. The quantity of faliva may alfo be increafed 

 beyond what is natural, by the catenation of the 

 motions of thefe glands with other motions, or feii- 

 fations, as by an extraneous body in the ear; of 

 which I have known an inflance; or by the applica- 

 tion of ftizolobium, filiqua hirfuta, cowhage, to the 

 feat of the parotis, as fome writers have affirmed. 



II. t. The lacrymal gland drinks up a certain, 

 fluid from the circumfluent blood, and pours it oh 

 the ball of the eye, on the upper part of the exter- 

 nal cornet of the eyelids. Though it may perhaps 

 be flimulated into the performance of its natural 

 udlion by the blood, -which furrounds its origin, or 

 by fome part of that heterogeneous fluid ; yet as the 

 tears fecreted by this gland are more wanted at fome 

 times than at others, its fecretion is variable, like that 

 of the faliva above mentioned, and is chiefly produced 

 when its excretory duel: is flimulated ; for in our 

 common fleep there feems to be little or no fecretion 

 of tears ; though they are occafionally produced by 

 our fenfations in dreams. 



Thus when any extraneous material on the eye- 

 ball, or the drynefs of the external covering of it, 

 or the coldnefs of the air, or the acrimony of fome 

 vapours, as of onions, Simulates the excretory duel: 

 of the lacrymal gland, it difcharges its contents upon 

 the ball ; a quicker fecretion takes place in the gland, 

 and abundant tears fucceed, to moiiten, clean, and 

 lubricate the eye, Thefe by frequent nictitation are 



VOL. I. Y diffufed 



