UPON THE VASCULAR SYSTEM. 



125 



Fig. 1. — Diagram showing innerva- 

 tion of Gastric Blood-vessels. 



stimulation of the afferent nerves of that part. There, however, he stopped. 

 He has advanced no theory regarding the bearings of this fact upon our con- 

 ceptions of the mode in which vascular dilatation in a part commonly takes 

 place, nor has he thrown out any suggestion as to the agent by which these 

 nerves are normally brought into play. I believe that the experiments which 

 I have yet to detail will be found to very decidedly advance our knowledge 

 regarding this matter. 



The vasomotor nerves for the blood-vessels of the stomach are contained in 

 the splanchnic nerves. The vaso-inhibitory and excito-vasomotor nerves of 

 that organ appear to me to be for the most part, if not entirely, contained in 

 the pneumogastric nerves. If it be true — as I imagine — that when the gastric 

 blood-vessels undergo dilatation, vaso-inhibitory nerves are brought into play, 

 we should — if these nerves be contained in the vagi — expect to find that if the 

 vagi be divided during dilatation of gastric blood-vessels, the vessels will undergo 

 contraction, and we should desire to see that stimu- 

 lation of the upper end of the divided nerve is able 

 to produce dilatation of vessels. In order that the 

 sequel may be better understood, I would refer the 

 reader to the following diagram representing the 

 stomach, s ; the vagus, v ; the splanchnic nerve, sp ; 

 the medulla oblongata, m. o.; and the spinal chord, 

 s. c. The arrow near the vagus indicates the direc- 

 tion in which vaso-inhibitory and vaso-excito motor 

 influences travel through the vagus to affect the vaso- 

 motor centre in the medulla oblongata — while the 

 arrow near the splanchnicus indicates the direction 

 in which vasomotor influences travel through that 

 nerve to the gastric blood-vessels. 



The following experiments were undertaken to 

 ascertain whether or not one can obtain evidence 

 of the passage of vaso-inhibitory influences through 

 the vagus during the dilatation of the blood-vessels of the stomach which takes 

 place during digestion, and also to ascertain the effect of irritating the vagus 

 upon the gastric blood-vessels : — 



m.o. 



Stomach, s. Spinal Cord, s.c. Me- 

 dulla Oblongata, m.o. Vagus, v. 

 Splanchnicus, sp. 



