RE PR OD UCTION. 465 



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 liquid 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. Bat all muscular and erectile activity, 

 as well as sexual passion, is usually 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 im- 

 mediately after copulation exerts a suction upon the liquid which aids in its 

 passage through the os and the cervix. It is possible that active contraction 

 of the vaginal walls assists. Spermatozoa have been found in the uterus a 

 half hour after coition. 1 The main agency in the locomotion of the sper- 

 matozoa through the body of the uterus and the Fallopian tubes, and prob- 

 ably 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 2 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 th<> 

 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 arc probably capable of living 

 within the genital passages for several days, when, if ovulation has not taken 



place, they perish. If, however, an ovum appears, they at •<■ approach and 



surround it in great numbers, being apparently attracted t<> it in some myste- 



1 Schuworski : Abstract in Monatsschrift fwr Oeburlshulfe nu<l Oynakologie, L896, iv. S. 275. 

 -II. Kraft: Pfiuger'i Archiv fur die gesammte Phyeiologie, f890, slvii. 



Vol.. II.— 30 



