258 THE PHYSIOLOGY OF REPRODUCTION 



contents into the vasa, and the mixed fluid passes out through 

 the ejaculatory ducts into the prostatic portion of the urethra. 

 The prostatic muscles also contract, and probably assist in 

 forcing the semen along the urethra, while at the same time 

 expelhng the secretion of the prostate glands. Entrance to the 

 bladder is prevented by the erection of the crista urethrse, assisted 

 by the contraction of the sphincter of the bladder, as already 

 mentioned. The final discharge is brought about by the 

 rhythmical contractions of the bulbo-cavernosus and ischio- 

 cavernosus muscles, which have the effect of emptying the 

 canal from behind forwards, and so ejecting the semen, mixed 

 with the various glandular secretions, into the vaginal passage 

 of the female. 



The innervation of the muscles of the penis has already been 

 described. 



The secretory cells of Cowper's glands receive branches from 

 the pudic nerves. 



The prostate is innervated by fibres coming both from the 

 nervi erigentes and from the hypogastric nerves. The former 

 are purely motor, whereas the latter are both motor and secretory. 

 Eckhard ^ found that stimulation of the nervi erigentes in the 

 dog caused the expulsion of the prostatic secretion into the 

 urethra. Loeb ^ obtained contraction of the prostatic vesicles 

 by excitation of • the hypogastric nerves. Mislawsky and 

 Bormann ^ confirmed both these observations, and found also 

 that stimulation of the hypogastrics, while inducing the muscles 

 to contract, at the same time promoted secretory activity in the 

 glandular cells, the secretion continuing so long as the stimula- 

 tion was kept up.* Fogge also states that he found hypogastric 

 stimulation to produce contraction of the prostatic muscles.^ 



' Eckhard, loc. cit. 



" Loeb (A.), " Beitrage zur Bewegung des Samenleiters, " Inaug. -Dissert., 

 Giessen, 1866. 



' Mislawsky and Bormann, " Die Secretionsnerven der Prostata," Zentralhl. 

 f. Phys., vol. xii., 1898. 



' Timofeew has described end-bulbs in the prostate, testis, and other 

 male genital organs. Some of these are of a peculiar kind, and are in 

 connection with two nerve-fibres (" Zur Keuntnis der Nervenendigungen in 

 den Mannliohen Geschlechtsorganen der Sanger," Anat. Am., vol. ix., 1894). 



^ Fogge, " On the Innervation of the Urinary Passage in the Dog," Jour, 

 of Phys., vol. xxviii. , 1902. 



