BY DR. LAUDER BRUNTON. 493 



** 131. Effect of Stimuli on the Secretion of Gastric 

 Juice. To see the effect of stimuli applied to the mucous 

 membrane, a dog with a gastric fistula should be allowed to 

 fast for six or seven hours, and then laid on its side in such a 

 position that a good light falls into the canula. The observa- 

 tion consists in noting the color of the membrane, and then in- 

 jecting a little dilute solution of sodium carbonate, or tickling 

 the surface with a feather, and observing the effect. The effect 

 of irritation on the amount of secretion may be estimated by 

 letting the dog stand while the beaker is held under the canula, 

 and by measuring the juice which flows from it in a given time 

 before and after irritation. 



** 132. Demonstration of the Action of the Vagus 

 and Splanchnic on the Stomach. The proof that the 

 vasomotor nerves of the stomach are derived from the splanch- 

 nics is founded on the observation that, when the left splanch- 

 nic is irritated in the rabbit, as directed at page 259, the arte- 

 ries at the great curvature may be seen to contract. This may 

 be still better seen in the cat. 



f The vagus is the sensory nerve of the stomach and contains k 

 Jafferent fibres, the irritation of which produces reddening oft 

 \the gastric mucous membrane. It also contains motor-fibres| 

 which are distributed to the muscular coats of the organ. Tor 

 show these facts, a cat must be placed under chloroform, after 

 which both vagi are prepared, and the stomach exposed. If, 

 now, the animal having partially recovered from the anaesthetic, 

 the stomach is seized between the thumb and forefinger, and 

 subjected to traction in the direction of its length, slight but 

 unequivocal signs of uneasiness are perceived. The vagi are 

 then divided, after which it may be observed, first, that the 

 stomach is paler than before, and secondly, no sign of uneasi- 

 ness is produced by traction. 



On irritation of the central end of one of the divided nerves, 

 the color of the mucous surface is more or less completely re- 

 stored. On irritation of the peripheral end, the walls of the 

 stomach often begin 10 contract, but this effect is not constant 

 when either splanchnic is intact. When both are divided, irri- 

 tation of either vagus is invariably followed by movements of 

 the stomach (Houckgeest). 



Experiments on vomiting have been omitted, as they do not 

 succeed in narcotized animals. 



it and causes vomiting, it appears probable that some of the gastric nerves 

 are more easily excited than others. See Carpenter's Physiology, edited 

 by Power, 7th edition, p. 128. 



