482 URO-GENITAL APPARATUS. 



nomenon which precedes and renders this act more efficacious, 

 viz. erection. 



A. Erection. 



The apparatus of erection is composed of the penis, its 

 cavernous body and its spongy body (also the bulb and glans). 



The object of erection consists in placing the urethral 

 canal in the most favorable posture for the easy flow of the 

 spermatic fluid, and for its transportation into the female 

 organs of generation. 



Erection is caused by a reflex action, whose point of origin 

 is in the brain (imagination), and in most of the organs of the 

 senses as well as in the sensitive surfaces ; but the excitation 

 of the mucous surface of the glans penis carries this reflex 

 action to its highest degree. Indeed, the glans is furnished 

 with numerous nervous papillae which gives to it a special 

 sensation, called genital ; the excitation of this sensibility is 

 the point of origin for that chain of acts which constitutes 

 coitus (erection, abundant secretion of sperm, excretion, 

 ejaculation), just as the excitation of the tauces is the signal 

 for the series of acts of deglutition. The dorsal nerve of the 

 penis is the centripetal path for these reflex phenomena, 

 which become impossible after section of this nerve, as at- 

 tested by many repeated experiments on horses. 



The question of the mechanism of erection is very com- 

 plicated, and upon it there is little agreement : it has been 

 demonstrated that this phenomenon essentially consists in 

 an accumulation of blood in the texture of the cavernous 

 and spongy portion of the erectile apparatus, but the embar- 

 rassment lies in the explanation as to how this blood is re- 

 tained, and at so high a tension. Yet a few circumstances 

 can clear up this study ; thus it is admitted that an erection 

 of the cavernous body is often independent of that of the 

 spongy portion of the urethra, and can result without genital 

 excitement, by a simple and mechanical opposition to the. 

 return of the venous blood ; to this kind of erection belongs 

 that produced when the bladder is distended with its fluid 

 contents ; this is followed by a compression of those venous 

 plexus which are formed by an expansion of the dorsal vein 

 of the penis (prostatic or plexus of Santorini, placed between 

 the bladder and pubis^. Fig. 129, p. 474). It is, then, prob- 

 able that when the erection is really active it produces upon 

 all the veins coming from the erectile parts a similar constric- 



