9 



That the heart is not stiumlated is cleai- from the fact that 

 the pulse is not api)reciably (juickened, and that the effect 

 is not general, hut local. Some facts may he of interest 

 concerning the effect of stimulus upon the blood vessels, 

 and the effect of a suspension of all stimulus. 



''When a person blushes the action of the nerves upon the 

 vessels of the cheek is temporarily suspeiided, causing them 

 to dilate." (Huxley and Youmans). 



"AVhen })ure alcohol is applied to the skin, after the tirst 

 effect of cold caused by its evaporation has [)assed off, the 

 part becomes red from temporary pared >/nis of the bJood 

 vessels, causing them to dilate." (Prof. H. N. Martin). 



"If the sympathetic nerve in the neck of a rabbit be di- 

 vided, a vascular congestion of all parts of the head on the 

 corresponding side immediately follows. The vessels of the 

 ear become turgid with blood." (Prof. J. C. Dalton). 



"Terror causes the skin to grow cold, and the face to 

 appear ^ja/e and pinched, the supply of blood to the skin is 

 greatly diminished in consequence of an excessive stliimla- 

 tion of the nerves of the small arteries which causes them to 

 contract.'' (Huxley and Youmans). 



It will be observed that in each of the tirst three examples 

 preceding the skin becomes reddened when there is no stim- 

 ulation ivhatever from the central nervous system, and in the 

 case of the rabbit all communication was entirely cut of from 

 ithy section of the nerve. The effect therefore oi a shs- 

 jjension of stimulation, is relaxation of the vessels, dilatation, 

 and redness ! If the blood vessels are really stimulaied by 

 an influence transmitted from the central nervous system as 

 Mr. Bergen implies, then it appears that the same effect is 

 produced when they are stinuilated, as when they are not ! 



The subject of nerves is a very difficult one, and notwith- 

 sbanding the increase of knowledge on the subject in recent 

 years, it is still far from being well understood. It is 

 known however that there are vaso-constrictor nerves which 

 contract the vessels, when stimulated, and vaso-dilator 



