304 THE ADRENAL, GENERAL MOTOR, AND VAGAL SYSTEMS. 



ment with the classic one just referred to, inasmuch as in the 

 latter we are dealing with an afferent impulse, followed ~by an 

 efferent impulse. The one experiment, therefore, confirms the 

 other, and we are brought to recognize that the vagus, as re- 

 gards its gastric functions, can transmit afferent impulses to 

 its center from the stomach and impulses from the center to 

 the stomach, the former being evidently sensory and the latter 

 motor. And, indeed, there is considerable testimony to the 

 identity of the vagus as a motor nerve, and, we may add, to 

 the presence of some exceedingly sensitive center in the region 

 mentioned, since marked excitement or emotion fear, anger, 

 etc. during digestion will sometimes arrest the latter: i.e., 

 give rise to the effect observed after section of both vagi. As 

 the motor nerves (ex-sympathetic) are efferent nerves, we 

 therefore have two efferent systems connected with the stomach 

 besides the sensory portion of the vagus referred to. 



What is the relationship between the vagus and the 

 plexuses overlying the cceliac axis? That the extrinsic vessels 

 are subject to contractile influences similar to those of the 

 organs already described is shown by the fact that, when all 

 nerves distributed to the stomach are cut, the secretion of 

 gastric juice becomes continuous. Relaxation of the vascular 

 supply having been induced, the secretion is doubtless due to 

 the ensuing engorgement of the blood-vessels and correspond- 

 ingly increased metabolism and temperature: a repetition of 

 the phenomena witnessed after section of the sympathetic else- 

 where. Again, that the intrinsic process in the mucous mem- 

 brane is also that witnessed in the organs referred to is shown 

 by the following lines by Professor Foster: "When the secre- 

 tion is very active, the blood flows from the capillaries into the 

 veins in a rapid stream without losing its bright arterial hue. 

 The secretion of gastric juice is, in fact, accompanied by vas- 

 cular dilation in the same way as is the secretion of saliva" 

 We can, therefore, assume that the cceliac-plexus extensions 

 fulfill precisely the same role that the sympathetic branches 

 we have termed "extrinsic vasoconstrictor" did in the other 

 organs, since they belong to the same motor system. 



What is the relative function of the two sets of nerves 

 in the gastric structures? To analyze this question a brief 



