REPRODUCTION IN MAN 1279 



FERTILISATION 



The act of impregnation consists in the introduction of spermatozoa 

 into the female genital tract, where they may come in contact with and 

 fertilise the ovum, which is discharged from the ovary by bursting of a 

 Graafian follicle. This is effected in the act of coitus or sexual congress by 

 the insertion of the penis into the vagina of the female. Before this can 

 occur erection of the male organ must take place. The mechanism of 

 erection js twofold. The most important factor, as was shown by Eckhard 

 and Loven, is an -active dilatation of the vessels of the penis, especially of the 

 medium-sized and smaller arteries. If the penis be cut across while in the 

 flaccid condition, venous blood merely trickles away from the cut surface, 

 whereas, if erection be excited, the flow of blood from the cut surface is 

 increased eight to ten times, and the blood becomes bright arterial in colour. 

 It is thus possible to excite erection in an animal, in whom the second factor 

 has been abolished by paralysing the muscles by means of curare. This 

 second factor is the contraction of the ischio-cavernosus or erector penis 

 muscle, certain fibres of which pass over the dorsal vein of the penis and 

 compress this vessel when they contract. Since ligature of the veins 

 coming from the penis does not produce erection, the contraction of this 

 muscle must be regarded as simply aiding the effects of the arterial 

 dilatation. 



Before or at the beginning of coitus analogous changes occur in the 

 female organs, leading to erection of the clitoris and of the erectile structures 

 of the vulva. The glands of the vulva, especially the glands of Bartholini, 

 secrete a mucous fluid, thus lubricating the passage into the vagina. The 

 friction between the glans penis and the wall of the vagina causes a reflex 

 discharge of motor impulses in both male and female (the/ orgasm '). In 

 the former the muscular walls of the vasa deferentia and seminal vesicles 

 enter into rhythmic contractions, thus forcing the spermatozoa they contain 

 into the urethra. The spermatozoa, mixed with the secretions of the 

 epididymis, the seminal vesicles, the prostatic glands, and the glands of 

 Cowper, form the semen, which is pressed along the urethra by rhythmical 

 contractions, from behind forwards, of the bulbo- and ischio-cavemosi 

 muscles. It has been stated that movements take place coincidently in the 

 uterus, so that its axis more nearly corresponds to that of the vagina. The 

 movement of the semen along the uterus and Fallopian tubes is ascribed by 

 certain observers to an antiperistaltic contraction of these organs. A more 

 important factor is probably the movement of the spermatozoa themselves. 

 As we have already seen, these are introduced into the female passage in 

 countless numbers. They will be chemiotactically attracted by the alkaline 

 mucus, secreted by and filling the cervix of the uterus. When they have 

 entered this organ they will meet the downward stream of mucus impelled 

 by the action of the cilia lining the uterus and Fallopian tubes. It seems 

 probable that their reaction to this current is to swim 1 against it (positive 



1 Spermatozoa move in a straight line, at the rate of 2 to 3 mm. per minute. Thus 



