156 PEACTICAL PHYSIOLOGY 



Stimulation of the chorda or injection of pilocarpine increases the 

 outflow of lymph 2J 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. 



CHAPTER XLIV. 

 GASTRIC AND PANCREATIC SECRETION. 



The Gastric Secretion is obtained by making an incision in the 

 stomach as in Fig. 138, and then reflecting and suturing the mucous 

 membrane of the stomach, so as to make a separate secreting sac 

 which is still in muscular and nervous continuity with the rest of 

 the stomach. The mouth of the sac is sewn to the opening in the 

 abdominal wall (Pawlow). The vagus is exposed ligatured and 

 divided. Three days later the peripheral end of the vagus is excited 

 in the unanaesthetised animal and the juice collected. 1 Anaesthesia or 

 operative procedures easily inhabit the gastric secretion. Pawlow opens 

 the gullet in the neck, and stitches the ends of the gullet to the open- 

 ing. The dog is then given meat. He eats it, and the meat falls out of 

 the opening in the gullet. This fictitious feeding, which the dog will 

 enjoy for an hour or so, reflexly excites secretion of gastric juice. 

 Mechanical excitation of the mucous membrane of the stomach does 

 not provoke secretion. 



The Pancreatic Secretion. In the anaesthetised dog the duct of the 

 pancreas is exposed where it lies on the duodenal wall and a cannula 

 inserted. A piece of the jejunum is excised, chopped up,and submitted 

 to the action of 0'4 per cent. HC1. This acid extract of jejunum on 

 being injected intravenously excites a copious secretion of the pancreatic 

 juice. Normally the acid of the gastric juice on coming in contact 



1 This experiment cannot be demonstrated. 



