652 



REPRODUCTIVE ORGANS. 



traction of the erector penis and bulbocavernosus muscles. The 

 result is the distention of the penis with blood, producing the rigid 



condition of that organ called erec- 

 tion. The verumontanum, which like- 

 wise contains erectile tissue, becomes 

 at the same time rigid, and assisted 

 by the contraction of the sphincter 

 vesicse, closes the passage to the 

 bladder. 



The clitoris of the female pos- 

 sesses an erectile structure, and during 

 coitus undergoes a change analogous 

 to that of erection in the male. 



Ejaculation. Some writers de- 

 scribe an ejaculatory center that is, 

 a special center in the spinal cord that 

 presides over the emission of semen 

 which constitutes ejaculation, while 

 others deny its existence. As a result 

 of the excitation produced by the act 

 of copulation the testicles become very 

 active in the formation of their secre- 

 tion, and this is carried to the ampullae 

 of the vasa deferentia by the muscular 

 action of the various portions of the 

 canal which it traverses. The mus- 

 cular coat of the seminal vesicles, and 

 that of the ampullations by their con- 

 traction expel their contents, the 

 semen, into the ejaculatory ducts, 

 through which it is discharged into 

 the prostatic portion of the urethra 

 (Fig. 438). Here are added to it the 

 secretion of the prostate, expelled by 

 the muscular tissue of that gland, and 

 the secretion of the glands of Cowper. 

 By the combined rhythmic action 

 of the ischio- and bulbocavernosi, constrictor urethra, external 

 sphincter ani, and levator ani muscles, the semen is forced through 

 the remaining part of the urethra and out of the meatus. 



During copulation the glands of Bartholin, situated on each 

 side of the commencement of the vagina and behind the hymen, 

 and which are regarded as the analogues of Cowper's glands in 

 the male, secrete a mucous fluid which is poured out upon the 

 vulva. 



By the vibratile movement of their tails or flagella the sper- 

 matozoa penetrate the os uteri, passing into the interior of the 



FIG. 437. Deep dorsal vein 

 and its tributaries : A, glaus ; B, 

 B', corpus cavern osum ; (7, section 

 of pubis, made slightly below the 

 symphysis. 1, Deep dorsal vein ; 



2, its origin behind the glans ; 3, 



3, its tributaries coming from 

 the corpus cavernosum and 

 corpus spongiosum ; 4, dorsal 

 vein, bifurcated and arranged in 

 a sort of plexus, subpubic plexus ; 

 5, plexus of Santorini ; 6, 7, an- 

 astomosis of superficial dorsal 

 vein with external pudic and 

 obturator (Testut). 



