1126 THE REPRODUCTIVE ORGANS 



of the larynx, while the legs, arms and other parts cease their often 

 very prolific growth and increase in compactness rather than in length. 



The Seminal Vesicles. The Semen. — Shortly before its entrance 

 into the prostatic urethra, the vas deferens receives a duct from the 

 vesicula seminalis, and is now known as the ejaculatory duct. Each 

 seminal vesicle is about 4 cm. in length, pyriform in shape, and oc- 

 cupies with its fellow-organ the under surface of the bladder, directly 

 behind the prostate gland. Its wall consists of an external fibrous 

 coat, a middle muscular coat and an internal mucous coat. The 

 mucosa is beset with numerous tubular albuminous glands which add 

 a stringy constituent to the semen, consisting chiefly of globulins. 

 Since the semen becomes more fluid upon standing, it seems that these 

 globular masses, which have been added to it by the seminal vesicles, 

 merely serve the purpose of giving a greater volume to it. In fact, in 

 some animals this material is made to clot through the agency of a 

 ferment derived from the prostate gland. Obviously, this would 

 tend to obstruct the orifice of the vagina and thus prevent the loss of 

 spermatozoa. But it cannot be said that the seminal fluid, plus the 

 spermatozoa and testicular secretion, constitutes the entire semen, be- 

 cause this medium receives in addition the products of the prostatic 

 and urethral glands. 



The prostate gland attains the size of a chestnut and consists of 30 

 to 50 lobules with 15 to 30 ducts which open near the orifice of the 

 ejaculatory duct. The prostatic secretion is thin, cloudy, slightly 

 alkaline, and contains albumin but no mucin. The urethral or Cow- 

 per's glands are represented by two small globular masses, one on each 

 side of the prostate, which empty their product into the cavernous 

 portion of the urethra. Their ducts measure 3 to 4 cm. in length. 

 Their secretion is alkaline and rich in mucin. Droplets of it appear 

 sometimes in the meatus urethrse after micturition or after sexual 

 excitement which has not actually led to an emission of semen. 



The semen is grayish-white in color, and possesses a mucilaginous 

 consistency. Its specific gravity varies between 1.027 to 1.040. Its 

 very characteristic odor is derived from the spermin of the prostatic 

 secretion. The amount discharged during one ejaculation varies 

 between 1 and 6 c.c. in accordance with the sexual activity of the indi- 

 vidual, and each emission may furnish as many as 223,000,000 of sper- 

 matozoa.^ These elements are formed constantly and are then stored 

 in the seminal vesicles and adjoining tortuous portion of the vas 

 deferens. The fact that the liquid here collected contains about 70,- 

 000,000 of spermatozoa per cubic centimeter, although only one of 

 them is sufficient to fertilize the ovum, shows how liberal and fixed 

 in its purpose nature actually is when the propagation of the species 

 is at stake. 



The Erectile Tissues of the Male. — The transfer of the semen into 

 the seminal receptacle of the female is made possible by the act of 

 1 Lode, Pfluger's Archiv, 1, 1891, 278. 



