REPRODUCTION. 903 



and the canal of the epididymis, and sweeps along the powerful muscular 

 walls of the vasa deferentia in the form of a series of peristaltic waves. The 

 seminal vesicles also contract, and the mixed fluid and spermatozoa are poured 

 through the ejaculatory ducts into the prostatic portion of the urethra. The 

 muscles of the prostate expel the prostatic fluid and help to pass the semen 

 onward. The glands of Cowper possibly add their contribution. But the 

 final urethral discharge is effected especially by powerful rhythmic contractions 

 of the already partially contracted striped muscles, viz. the ischio- and bulbo- 

 cavernosi, the constrictor urethrce, and probably the anal muscles, the result of 

 the complex series of actions being to expel the semen with some force into 

 the upper part of the vagina close to the os uteri. Ejaculation is a reflex act. 

 The centre lies in the lumbar spinal cord ; the centripetal nerves are the sen- 

 sory nerves of the penis, stimulation of the glans being especially effective ; 

 the centrifugal nerves are the nerves to the various muscles. In the female 

 during ejaculation the glands of Bartholini pour out a mucous fluid upon the 

 vulva. There is possibly a downward movement of the uterus, brought about 

 by contraction of its round ligaments and accompanied perhaps by a contrac- 

 tion of the uterine walls themselves. But all muscular and erectile activity, 

 as well as sexual passion, is less pronounced in woman than in. man. 



Locomotion of the Spermatozoa. The union of the spermatozoon and the 

 ovum probably takes place usually in the Fallopian tube not far from its ovarian 

 end, and to this place the spermatozoa at once proceed. Their mode of entrance 

 into the uterus is not wholly clear ; it is quite generally believed, but without 

 conclusive experimental proof, that relaxation of the uterus immediately after 

 copulation exerts a suction upon the fluid which aids in its passage through 

 the os and the cervix. It is possible that active contraction of the vaginal 

 walls assists. However these may be, the main agency in the locomotion of 

 the spermatozoa through the body of the uterus and the Fallopian tubes, and 

 probably also from the vagina into the uterus, is the spontaneous movement of 

 the spermatozoa themselves. By the lashing of their tails they wriggle their 

 way over the moist surface, being stimulated to lively activity probably by the 

 opposing ciliary movements in the epithelium lining the passages. Kraft 1 has 

 shown in the rabbit that, when spermatozoa in feeble motion are placed upon 

 the inner surface of the oviduct, not only are they thrown into active contrac- 

 tions, but they move against the ciliary movement, i. e. up the oviduct. The 

 capacity of the male cells thus to respond by locomotion in the opposite direc- 

 tion to the stimulating influence of the ciliary cells over which they have to 

 pass, is an interesting adaptation. Probably this is the directive agency that 

 enables the spermatozoa to follow the right path to the ovum, while the ovum, 

 being in itself passive, is by the same ciliary movement brought toward the 

 active male cell. The time occupied in the passage of the spermatozoa is un- 

 known in the human female, but is probably short ; in the rabbit spermatozoa 

 have been known to reach the ovary within two and three-quarter hours after 

 copulation. As has been seen, spermatozoa are probably capable of living 



1 H. Kraft : Pfliiger's Archivfilr die gesammte Physiologic, xlvii., 1890. 



