ELEMENTARY EXPERIMENTAL PHYSIOLOGY 213 



1-2 mgrms., produces prolonged and plenteous secretion. The anta- 

 gonism may be shown by injecting atropine into the blood and then 

 injecting a little 2 per cent, solution of pilocarpine into the gland by 

 way of the duct cannula. 



If the duct cannula is connected with a mercury manometer and the 

 chorda tympani stimulated, the secretory pressure will be observed to 

 rise higher than the pressure in the carotid artery. 



The submaxillary gland has been placed in a plethysmograph and its 

 volume recorded (Bunch). Stimulation of the cervical sympathetic 

 causes very considerable diminution in volume and a scanty secretion. 

 Excitation of the chorda tympani is followed by diminution in volume 

 in spite of vaso-dilatation. This is due to the copious secretion. 

 After injection of atropine the volume is increased by chorda excitation. 



When a cannula was placed in the cervical lymphatic just above where 

 it enters the thoracic duct the effect of stimulating the salivary gland on 

 the outflow of lymph was observed (Bainbridge). 



Stimulation of the chorda or injection of pilocarpine increases the 

 outflow of lymph 2 times. If Wharton's duct be obstructed the 

 lymph flow is not so great. After injection of atropine no such 

 increase is found. Stimulation of the sympathetic also increases the 

 flow of lymph. 



When a permanent salivary fistula is made, and the duct cannula is 

 arranged to empty into a vessel attached to the dog's neck, it is found 

 that the character of the secretion varies with the nature of sensory 

 excitation (Pawlow). Stones placed in the dog's mouth are rejected 

 without flow of saliva. Sand is washed out by watery saliva which 

 contains almost no solid or ferment. Food provokes the secretion of 

 saliva rich in ferment. The reflex and sub-conscious nervous mechanism 

 which controls the secretion of saliva thus carries out actions which are 

 similar to voluntary or willed actions. 



