GENITAL SYSTEM. 483 



tion, either by contraction of the walls of the veins, or of the 

 numerous layers of smooth muscles through which these veins 

 pass before entering the pelvis (the middle layer of the peri- 

 neal fascia are almost entirely composed of smooth muscular 

 fibres) ; this would tend to arrest the blood in the texture 

 of the spongy tissues, and so produce a pressure equal to that 

 of the arterial blood. 



In this way erection depends upon a reflex contraction 

 which arrests the progress of blood in the veins ; and, in 

 fact, a pathological erection observed in dead subjects is 

 associated with clots which fill the veins of the erectile tissue 

 and extend to the veins of the pelvis ; this would seem to 

 prove that the compression occurs in the pelvic cavity. 



Perhaps, also, vaso-motor paralysis (see p. 170, Circulation) 

 has a certain influence upon the mechanism of erection, by 

 allowing the erectile tissues to be distended with the afflux 

 of blood ; yet it is evident that if the path for the return of 

 the venous blood should remain freely open, the vaso-motor 

 paralysis would not be sufficient for the production of a true 

 erection, and would only induce a more or less pronounced 

 turgescence. 



Professor Rouget 1 has established that in all cases there 

 exists a dilatation of the small arteries ; this same effect is 

 observed in the hypersemia of the ovary and the uterine 

 raucous surface at the commencement of the act of menstru- 

 ation, and is due, in his opinion, to the same causes as blush- 

 ing and the reddening of the crest or comb of the male fowl 

 called the cock. Finally, direct observation of the com- 

 mencement of the erection of the organs of copulation, and 

 the experiments of Eckhard on the paralysis of the small 

 arteries of the cavernous and bulbous portions of the urethra 

 after irritation of the nervi erigentes / both of these phenom- 

 ena prove that paralysis and vascular dilatation are the initial 

 phenomenon of all, even the most complicated kind of erec- 

 tion. 2 



But this phenomenon, though sufficient to prove the 



1 Ch. Rouget, " Recherches sur les Organes Erectiles de la 

 Femme." ("^Journal de Physiologie," Vol. I., 1858.) " Des 

 Mouveraerits Erectiles." (Ibid., 1868.) 



2 Thus we can call to mind in view of erection all that has been 

 said in regard to the physiology of the vaso-motor nerves. To 

 this class of phenomena belong the theory of active dilatation of 

 Schiff, and the peristaltism of the blood-vessels of Legros aud Oni- 

 mus (see Vaso-motors, pp. 173 et seq.). 



