GENITAL SYSTEM. 481 



and the vas deferens (E', C d} by means of the vis a tergo 

 and by contractions of the muscular fibres in these canals. 

 Venereal excitations singularly hasten its production and 

 secretion ; but when these excitations are repeated at too 

 short intervals, the spermatic fluid has no time to be 

 thoroughly elaborated, and hence the sperm atozoids are often 

 found in the ejaculated secretion still enveloped in their 

 mother cells. 



In its course from the testicle to the prostatic region, the 

 sperm may turn aside into the vesiculcB seminales (Fig. 131, 

 v s), which might be looked upon as a diverticulum of the 

 vas deferens (spermatic duct) analogous to the vas aberrans 

 (Fig. 131, Va), which are derived from the lateral cceca 

 of the Wolffian body; but the function of a spermatic reser- 

 voir assigned to the seminal vesicles has never been perfectly 

 demonstrated : most often there has only been found in this 

 diverticulum a yellowish mucus, which apparently, in the 

 same way as the prostate and Cowper's glands, gives to the 

 sperm a more fluid character. The red globules of the blood 

 are frequently found in the product of the seminal vesicles, 

 especially when there has been no coition for a long time 

 (Ch. Robin), but their presence need cause no alarm. The 

 concretions which are found in these products are proved 

 by their chemical properties to be formed of the nitro- 

 genous concrete mucus. The seminal vesicles are not found 

 in a large number of the lower animals, especially not the 

 dog. 



By peristaltic movements of the efferent system, the sper- 

 matic fluid is thrown along the ejaculatory ducts into the 

 prostatic portion of the urethra ; these ducts lead from the 

 seminal vesicles and the termination of the vas deferens 

 towards the posterior wall of the urethra (Fig. 131, p. 479). 

 Then they pass through the posterior half of the prostate 

 gland. In spite of the name ejaculatory^ these ducts take no 

 active part in this mechanical phenomenon : their thin walls, 

 which are nearly devoid of muscular elements, would not 

 allow of any active contraction. They serve only to conduct 

 the sperm to the prostatic region, at which latter place its 

 contact with the sensitive mucous surface excites a peculiar 

 reflex action, the ejaculation, whose mechanism it is ex- 

 tremely difficult to study, but which is destined to project 

 the male fecundating fluid into the female organs of gener- 

 ation. We shall first proceed to the consideration of a phe- 



31 



