REPRODUCTION. 237 



of the base of the bladder, where it unites with the duct of the vesicula semin- 

 alis to form the ejaculatory duct. 



The vesiculae seminales are two lobulated, pyriform bodies about two 

 inches in length, situated on the inner surface of the bladder. 



They have an external fibrous coat, a middle muscular coat, and an internal 

 mucous coat, covered by epithelium, which secretes a mucous fluid. The 

 vesiculae seminales serve as reservoirs, in which the seminal fluid is tem- 

 porarily stored up. 



The ejaculatory duct, about of an inch in length, opens into the 

 urethra, and is formed by the union of the vasa deferentia and the ducts Of 

 the vesiculae seminales. 



The prostate gland surrounds the posterior extremity of the urethra, and 

 opens into it by from twenty to thirty openings, the orifices of the prostatic 

 tubules. The gland secretes a fluid which forms part of the semen and 

 assists in maintaining the vitality of the spermatozoa. 



Semen is a complex fluid, made up of the scretions from the testicles, the 

 vesiculae seminales, the prostatic and urethral glands. It is grayish-white in 

 color, mucilaginous in consistence, of a characteristic odor, and somewhat 

 heavier than water. From half a dram to a dram is ejaculated at each 

 orgasm. 



The spermatozoa are peculiar anatomic elements, developed within the 

 seminal tubules, and possess the power of spontaneous movement. The sper- 

 matozoa consist of a conoid head and a long, filamentous tail, which is in 

 continuous and active motion; so long as they remain in the vas deferens 

 they are quiescent, but when free to move in the fluid of the vesiculae semi- 

 nales, they become very active. 



Origin. The spermatozoa appear at the age of puberty, and are then 

 constantly formed until an advanced age. They are developed from the 

 nuclei of large, round cells contained in the anterior of the seminal tubules, 

 as many as fifteen to twenty developing in a single cell. 



When the spermatozoa are introduced into the vagina, they pass readily 

 into the uterus and through the Fallopian tubes toward the ovaries, where 

 they remain and retain their vitality for a period of from eight to ten days. 



Fecundation is the union of the spermatozoa with the ovum during its 

 passage toward the uterus and usually takes place in the Fallopian tube 

 just outside the uterus. After floating around the ovum in an active manner, 

 a single spermatozoan penetrates the ovum, this accomplished, the head and 

 body meet and unite with the nucleus of the ovum. A series of histologic 

 changes now arise which eventuate in the production of a new cell, the parent 



