988 THE PHYSIOLOGY OF REPRODUCTION. 



swelling and congestion of the membrane constitute a prepara- 

 tion for the reception of the fertilized ovum. If the ovum fails of 

 fertilization, then degenerative changes ensue, and the membrane 

 or a portion of it is cast off in the menstral flow, while the re- 

 mainder is absorbed. According to this view, menstruation is an 

 indication that fertilization has not taken place.* This view 

 falls in with the belief that ovulation normally precedes menstrua- 

 tion by a considerable interval. A modification or extension of 

 this general hypothesis is proposed by Bryce and Teacher. f 

 They believe that the process of menstruation is a cyclic one, 

 which has for its object the preparation of the endometrium for 

 the reception of the ovum. The monthly regeneration keeps 

 this membrane in that condition of youthful irritability which 

 enables it to respond promptly to the stimulus of the ovum by 

 the formation of a decidua. The other point of view was advo- 

 cated especially by Pfluger in connection with his theory of a 

 common cause of ovulation and menstruation. He assumed that 

 menstruation occurs before the ovum reaches the uterus and that 

 its physiological value lies in the fact that a raw surface is thus made 

 upon which the ovum is grafted. Menstruation, according to him, 

 is an operation of nature for the grafting of the fertilized ovum 

 upon the maternal organism. This view finds considerable support 

 in the fact that in some of the lower animals (dogs) the flow of 

 blood (prooestrum) ' precedes fertilization. 



The Effect of the Menstrual Cycle on Other Functions. It 

 is natural to suppose that such marked changes as occur in the 

 ovary and uterus during the menstrual cycle should have an in- 

 fluence upon other parts of the body. As a matter of fact, it is 

 known that in general the sense of well-being varies with the phases 

 of the cycle. At the time of or in the period just preceding the 

 menstrual flow there is usually a more or less marked sense of ill- 

 being or despondency, and a diminution in general efficiency. 

 Efforts have been made to explain these subjective changes gn the 

 assumption that the body processes may undergo wave-like 

 variations corresponding with the menstrual cycle. J The numer- 

 ous reports made prove in general that the body temperature and 

 pulse-rate do show such a wave moment, reaching a maximum 

 just before menstruation and falling to a minimum shortly after 

 menstruation. The changes, however, are very slight and hardly 



* This view finds expression in the aphorisms: "Women menstruate 

 because they do not conceive," Powers, and "The menstrual crisis is the 

 physiological homologue of parturition," Jacobi. 



f Bryce and Teacher, "Early Development and Imbedding of the Human 

 Ovum," 1908. 



J Jacobi, "Boylston Prize Essay The Question of Rest for Women 

 during Menstruation," 1876. 



