174 THE BLOOD AND ITS CIRCULATION. 



tary contraction for the diastole observed in the uninjured 

 animal is much greater than can be produced by section of 

 the great sympathetic nerve, in other words, by paralytic 

 dilatation. The diastole observed would be then really an 

 active dilatation. 



Irritation of the central extremity of the auriculo-cervical 

 nerve (auricular branch of the cervical plexus) produces, by 

 a reflexive course, dilatation of the vessels of the ear; this 

 the same experiments prove to be an essentially active, not 

 paralytic phenomenon (there is no contraction of the veins, 

 paralytic dilatation). 



Vaso-motor reflexes (reflex actions) of a similarly active 

 nature, and more powerful in effect than the paralyzing in- 

 fluences, have been observed by Schiff, by placing the animal 

 (dog or rabbit) in a vapor-bath, or producing in it a septic 

 fever, exciting its passions, etc. 



Finally, Schiff ascertained that irritation of the peripheral 

 extremity of the auricular branch of the trifacial imme- 

 diately produces these active dilations ; one of these nerves, 

 like the chorda tympani, acting upon these organs in such a 

 manner as to produce in them functional hypercemia, which 

 Schiff prefers to distinguish from neuro-paralytic hypercemia, 

 without, however, denying the existence and importance of 

 the latter. 



The theory of the peristaltism of the arteries is more com- 

 plete; it seeks to explain normal as well as pathological 

 facts, and enters into the closest details of the question. 

 Legros and Onimus ground this theory on investigations of 

 three kinds : 



1. Direct inspection of the small arteries discloses vermic- 

 ular or peristaltic contractions, beginning in the principal 

 trunks, extending to the smallest arteries, and assisting the 

 progress of the blood. Goltz and Thiry had already ascribed 

 to a similar mechanism the evacuation of the arteries after 

 death. Onimus observed these movements in the vessels of 

 the inferior animals (annelida), in which their existence had 

 long been recognized, but he has besides pointed them out in 

 the interdigital membrane in frogs, and even in man in the 

 email arteries of the eye: "if the central artery of the retina 

 be obstructed by a clot, we see, by the aid of the ophthal- 

 moscope, that the small arteries, which show the existence 

 of a collateral circulation, have very marked peristaltic 



