SYMPATHETIC. 



333 



vagus effect may come on simultaneously at all points of the small 

 intestine, and is not abolished by ligaturing the second part of the 

 duodenum or the upper part of the jejunum. The vagus fibres must 

 therefore reach the intestine at all points, and do not run down from 

 the stomach or duodenum between the two coats. The effects are better 

 marked in those portions of the intestine which are already excited by 

 the presence of a bolus or of a balloon for the purpose of recording the 

 movements. 



We must conclude, therefore, that the vagus contains two sets of 

 fibres to the muscular coat of the intestine one set inhibitory, 

 with a very small latent period ; the other set augmentor or motor, 

 with a very long latent period. The action of the latter can be easily 

 prevented by the presence of inhibitory influences acting on the intestine 

 at any point. 



Sympathetic. The main sympathetic supply reaches the intestines 

 by means of the splanchnic nerves. Pfluger 1 was the first to show 



FIG. 188. Curve showing inhibitory effect on contractions of small intestine, of stimulat- 

 ing peripheral end of right splanchnic nerve. The middle line shows the duration 

 of stimulation. Time marking = six-second intervals. Balloon method. 



that the stimulation of these nerves inhibits the intestinal movements. 

 This observation has been confirmed by almost every subsequent 

 observer, though there has been considerable discussion as to the exact 

 mode in which the inhibitory action is brought about. It has been 

 already pointed out that anaemia of the intestines checks the movements, 

 and S. Mayer and v. Basch 2 ascribed the inhibitory action of the splanch- 

 nics to their vaso-constrictor influence on the intestines. According 

 to v. Braarn Houckgeest, this view is negatived by the following experi- 

 ment. The intestines of a rabbit are exposed to the air until they 

 become reddened by vasomotor paralysis. Stimulation of the splanch- 

 nics now has no effect on the blood vessels. The movements of the 

 intestines, however, are inhibited, as in a normal animal. Jacobi 

 states that the intestinal inhibitory fibres of the splanchnics take a 



1 "Ueber d. Hemmungsnervensystem f. d. peristaltischen Bewegungen d. Gedarme," 

 Berlin, 1857. 



2 Sitzungsb. d. Ic. Akad. d. Wissensch., math.-naturw. Cl., Wien, 1870, Bd. Ixii., 

 Abth. 2, S. 811. 



