MALE ORGANS OF REPRODUCTION 479 



oogonial, primary and secondary, characterized by extensive prolifera- 

 tion. The primary oocyte divides in a manner similar to the primary 

 spermatocyte, that is by heterotypic mitosis, but the daughter-cells are 

 very unequal in size, each, however, with the same number of chromo- 

 somes (18) ; the small abortive cell is called the polar body, or better 

 polocyte, while the large cell becomes a secondary oocyte. Both polocyte 

 and secondary oocyte again divide, the end result being three similar 

 polar bodies and one large ootid or mature ovum, now ready for fertili- 

 zation. It must be recalled that the maturation process is in essence a 

 process of eliminating one-half of the original quota of chromosomes, 

 and a quantitative reduction of its original amount of chromatin to 

 one-fourth. At fertilization, by fusion of egg and sperm, the specific 

 number of chromosomes is reestablished differing in many cases in 

 male and female of the same species and the chromosomes by growth 

 regain or even exceed their original size. With this brief consideration 

 of the function of the germ glands in general, we may proceed to a 

 description of the structure of the male organs of reproduction and 

 subsequently of the female organs. 



MALE ORGANS OF REPRODUCTION 



These organs include the penis and the testes, together with their 

 accessory glands, and the excretory ducts which connect the testes with 

 the urethral canal. The excretory ducts include the epididymis, ductus 

 (vas) deferens, seminal vesicles, and ejaculatory ducts, and with their 

 termination in the urethra there are connected the ducts of the prostate 

 gland and the bulbo-urethral glands (of Cowper), whose secretion mixes 

 with that of the testes to form the semen. The male urethra serves the 

 double function of a urogenital canal. 



INTERNAL GENITAL OKGANS 

 Testis 



The testis is to be regarded as a gland with a double function ; it 

 produces cells (spermatozoa), hence a cytogenic gland; and an internal 

 secretion, hence, in part an endocrin gland. In connection with the 

 testis must be considered also its excretory duct system, and the various 

 glands accessory to it. The relationship of these various structures 

 is shown in diagram, Fig. 418. 



