1018 THE NERVOUS SYSTEM 



and the inferior vesical nerves, which supply the lower part of the bladder and, in the 

 male, give secondary deferential plexuses to the vas deferens. These plexuses sur- 

 round the vasa dei'erentia and the vesiculse seminales and anastomose with the 

 spermatic plexuses. 



The prostatic plexus, found only in the male, is formed in two parts by nerves 

 of considerable size, and lies chiefly on the sides of the prostate gland between it and 

 the levator ani (fig. 722). Each of these parts supplies the gland and the prostatic 

 part of the urethra, and sends offsets to the neck of the bladder and the vesiculae 

 seminales. This plexus is continued forwards on either side to form the cavernous 

 plexus of the penis (fig. 722), which anastomoses with branches of the dorsal nerve 

 of the penis, gives off branches to the membranous part of the urethra, and also 

 gives origin to two sets of nerves, namely, the large and the small cavernous nerves of 

 the penis. 



The large cavernous nerve, one on each side, runs forwards to the middle of the 

 dorsum of the penis, where it anastomoses with the dorsal nerve of the penis on the 

 corresponding side, and ends in twigs which are distributed chiefly to the corpus caver- 

 nosum penis, but some of the terminal filaments supply the corpus cavernosum 

 urethrae (corpus spongiosum) (fig. 722). 



The small cavernous nerves are small filaments which pierce the uro-genital 

 trigone (triangular ligament) and the compressor urethrae, and enter the posterior 

 part of the corpus cavernosum. 



The plexus utero-vaginalis, found in the female, is formed in its upper part on 

 each side largely by fibres derived from the pelvic part of the hypogastric plexus, but 

 it receives some fibres from the pelvic splanchnics of the third and fourth sacral 

 nerves. The nerves from this part of the plexus accompany the uterine arteries as 

 they pass between the layers of the broad ligament. Some accompany each uterine 

 artery and its branches to their termination, but a considerable number of fibres 

 leave the artery and pass into the body of the uterus to supply its lower part and 

 cervix. Between the layers of the broad ligament this plexus anastomoses with 

 the ovarian plexus and sends some filaments to the tuba uterina (Fallopian tube). 

 The lower part of the plexus utero-vaginalis receives some fibres on each side from 

 the pelvic part of the hypogastric plexus, but it is formed chiefly by efferent 

 splanchnic fibres from the second, third, and fourth sacral nerves. It supplies the 

 wall and mucous membrane of the vagina and urethra. From the plexus on the 

 anterior surface of the vagina fibres pass to form the cavernous plexus of the 

 clitoris, which gives off the great and lesser cavernous nerves of the clitoris for 

 the supply of the clitoris. The utero-vaginal plexus of the female corresponds to 

 the prostatic plexus of the male. 



