20 INTRODUCTION TO SEXUAL PHYSIOLOGY 



are ejaculated. The epididymis serves as the main storehouse 

 of the spermatozoa prior to ejaculation. 



The vas deferens is the duct which conveys the semen (or fluid 

 containing the spermatozoa) from the epididymis to the common 

 urogenital passage or urethra. It is lined internally by columnar 

 epithelial cells and its wall contains smooth muscle fibres which 

 contract in peristaltic waves when the semen is ejaculated. 



The semen ejaculated through the penis, which contains the 

 urethral channel, is the secretory product of the testes, epididymes, 

 vesiculse seminales, and other accessory glands. The vesiculce 

 seminales are situated at the end of the vasa deferentia, and 

 open on each side by a common duct (formed by the union of the 

 vas with the duct of the vesicle) into the urethra, which is the 

 urogenital passage. Into this the bladder also opens. It was 

 formerly supposed that the vesicles acted as seminal reservoirs, 

 but even in such animals as the hedgehog, in which they undergo 

 a very great development at rut, they do not contain spermatozoa. 

 In those cases where spermatozoa have been found in the vesicular 

 of human corpses, it is believed that entry took place after death, 

 owing to the relaxation of the muscles in the walls of the ducts. 

 It would seem probable that one of the functions of the vesiculae 

 is to contribute to the secretion of the medium for the trans- 

 ference of the spermatozoa. At the same time, it is possible that 

 the secretion has a nutritive function for the spermatozoa, or it 

 may exercise a stimulatory action such as has been postulated 

 for the prostatic secretion. In the hedgehog the vesiculse contain 

 a large quantity of glairy, milky fluid with much crystalloid 

 material which Hopkins has shown to consist of a peculiar kinrl 

 of phospho-protein. In rodents the secretion of the vesiculae 

 after ejaculation coagulates and forms a plug which prevents the 

 escape of the spermatozoa from the vagina of the female. The 

 ferment which causes the coagulation is formed by a separate 

 gland. The ducts of the vesiculse unite on each side \\'ith the vasa 

 deferentia and, as already stated, form the ejaculatory ducts 

 which pierce the prostate gland and open into the urethra. The 

 latter starting at the urinary bladder bends round the peh'ic 

 symphysis and is continued within the penis. 



The prostate is a tubular gland surrounding the urethra at 

 the base of the bladder and between that and the penis. It 

 communicates with the floor of the urethra by numerous small 



