REPRODUCTION 1005 



epithelium into the subepithelial connective tissue becomes fixed in 

 one of the crypts or pouches of the uterine mucous membrane 

 (decidua serotina], which grows round it as the decidua reftexa. 



Menstruation. In the mature female, from puberty, the age at 

 which the reproductive power begins (thirteenth to fifteenth year), 

 on till the time of the menopause (fortieth to fiftieth year), at which 

 it ceases, an ovum or it may be in some cases more than one is 

 discharged at regular intervals of about four weeks. This discharge 

 is accompanied by certain constitutional symptoms and local signs 

 that last for a variable number of days. The genital organs are 

 congested, and a qup.ntity of blood, which varies in different indi- 

 viduals, but is usually not over 50 c.c., is shed. If more than 60 c.c. 

 is lost the flow is copious. Over TOO c.c. it is abnormally great 

 (G. Hoppe-Seyler) . At the same time, the whole or a portion of the 

 mucous membrane of the uterus is cast off. 



As to the physiological meaning of this menstruation, .as it is 

 called, opinion is divided. Two chief theories have been proposed 

 to account for it, both of which agree in considering the phenomenon 

 to be connected with a preparation of the uterus for the reception 

 of the ovum. But according to the theory of Pfliiger the mucous 

 membrane is stripped off (by a process analogous to the ' freshening ' 

 or paring of the indurated edges of a wound by the surgeon, in 

 order that union may occur when they are brought together) on 

 the chance, so to speak, that an impregnated ovum may arrive. On the 

 alternative theory, this change takes place because the ovum has not 

 been impregnated, and the bed prepared for it not being required, 

 the swollen and congested uterine mucous membrane undergoes 

 degeneration, and is in part cast off (Reichert, Williams, etc.). 



The process of menstruation, and the nutrition of the genital 

 organs, especially the uterus, are intimately dependent upon the 

 ovaries. There is good evidence that the influence is exerted through 

 an internal secretion formed by some portion of the ovarian sub- 

 stance. When, for instance, the ovaries of young animals (guinea- 

 pigs) are removed from their normal situation and transplanted to 

 a distant part of the body, the external genitals, vagina, and uterus 

 undergo the normal development instead of being arrested in their 

 growth, as is the case when the ovaries are removed altogether. The 

 removal of the ovaries in adult animals leads to fibrous degeneration 

 of uterus and Fallopian tubes. On the other hand, removal of the 

 uterus has no effect on the development of the ovaries in a young 

 animal, and does not cause degeneration of the ovaries of an adult 

 animal. In monkeys, in which a menstrual flow comparable to that 

 in the human female occurs, it was found that menstruation took 

 place after the ovaries had been transplanted from their original seat, 

 and the flow stopped when the transplanted ovaries were removed. 

 It has been stated, too, that in a young woman suffering from 

 amenorrhcea (lack of menstruation) a regular flow appeared after 

 the transplantation of an ovary from another woman into her uterus. 

 Recently the view has been put forward that the important part of 

 the ovary for these functions is the corpus luteum, which is by some 

 investigators considered to be a gland with an internal secretion 

 (Born) . This secretion seems to be connected with the implantation 

 of the ovum and the subsequent growth of both ovum and uterus. 

 According to Fraenkel, the absence of the corpus luteum prevents 

 implantation. When the ovum has not been fertilized the corpus 

 luteum brings about menstruation. Where fertilization has occurred 



