844 THE PHYSIOLOGY OF REPRODUCTION. 



turn of the menstrual periods which had ceased after surgical re- 

 moval of the glands, or brought on free menstruation in conditions 

 of amenorrhea or dysmenorrhea. 



Many views have been proposed to explain this relationship 

 between ovary and uterus. In most cases it has been assumed 

 that the menstruation in the uterus is connected with the act of 

 ovulation, that is, the ripening and discharge of a Graafian follicle. 

 Gynecologists, it is true, have accumulated facts to show that ovu- 

 lation may occur independently of menstruation, but no one doubts 

 that, as a rule, the two acts occur together, not simultaneously but 

 in a definite sequence, and that the significance of menstruation is to 

 be found in its physiological dependence upon the fate of the ovum. 

 It was believed at first that the processes in the ovary influence the 

 uterus by a nervous reflex. This view finds its most complete 

 expression in the theory formulated by Pfliiger. According to this 

 physiologist, the congestion of the uterus which leads to menstrua- 

 tion and the congestion of the ovary which leads to ovulation are 

 both reflex vasodilator effects due to the mechanical stimulation 

 of the sensory nerves of the ovary by the growth in size of the fol- 

 licle. As this structure develops the mechanical stimulus increases 

 in intensity, the congestion in both organs becomes more pro- 

 nounced and leads finally to the bursting of the follicle and the 

 hemorrhage in the uterus. This very attractive theory does not, 

 however, accord with the facts. Goltz and Rein* have shown by 

 experiments upon dogs that when the nerves going to the uterus 

 are completely severed from their central connections the animals 

 can be fertilized, become pregnant, and give birth to a litter of 

 young. Moreover, the experiments upon transplantation referred 

 to above seem to show quite conclusively that a nervous connection 

 is not essential to the influence that the ovary exerts upon the 

 uterus. The present view, therefore, is that this influence is exerted 

 through the blood, the other great system connecting the organs 

 with one another. The usual assumption is that the ovaries form an 

 internal secretion which is given to the blood or lymph and upon 

 reaching the uterine tissues serves to stimulate the mucous mem- 

 brane to a more active growth. This theory has been elaborated 

 most fully perhaps by Fraenkel,t who believes that this internal 

 secretion is furnished by the yellow cells of the corpus luteum. 

 This observer, from the results of operations upon women, believes 

 that the ovum is normally discharged two weeks before menstrua- 

 tion, and the resulting increased activity of the cells of the corpus 



* Rein, " Archiv f . die gesammte Physiologie, " vol. xxiii. 



f Fraenkel, ' Archiv f. Gynakologie," 68, 2, 1903. See also Ihm, " Monats- 

 schrift f. Geburtshulfe u. Gynakol.," 21, 515, 1905, for discussion and exten- 

 sive literature. 



