590 HERBEET M. EVANS 



be healed over. In some of the mammals with cyclic oestrus, and as Long 

 and I have seen to be the case in the rat, a similar beginning fatty degen- 

 eration of the corpus luteum is coincident with the new oestrus cycle so 

 that we may also view the same event as inaugurating the cycle in man. 

 In the latter case, however, uterine growth changes cannot be immediately 

 produced, for the first part of the new cycle is occupied by the degeneration 

 and removal of old tissues produced by action of the corpus formed in the 

 preceding cycle. Only when this necrosis is complete and the tissue debris 

 removed can the endometrium again begin its cyclic growth. 18 



It does not need to be emphasized that these newer considerations neces- 

 sarily lead us to abandon the terminology and, what is more important, 

 the concepts which have previously existed in the literature on menstrua- 

 tion. The endometrial changes should be not be designated premenstrual, 

 for they are obviously not formed in order to necrose; they are more 

 properly termed pregravid. Nor can we speak of menstruation as a normal 

 process or as a "menstrual mechanism." The whole mechanism of these 

 changes in the reproductive tract is gauged for another event, i. e., preg- 

 nancy, and menstruation represents the failure of this contrivance and is 

 more properly viewed as a pathological event. Furthermore, our knowl- 

 edge that menstruation does not occur when a corpus luteum is functional 

 either in the normal cycle or, for example, during pregnancy should not 

 lead us to the conception of Seitz and Wintz, Kohler and Hjalban, Reusch, 

 and others, who speak of the "menstruation repressing" action of the 

 corpus. The former observers believe they allay uterine hemorrhage by 

 the administration of certain lutein extracts and the latter explain the 



18 The reader will have seen that the comparison between menstrual and oestrous 

 cycles which we have instituted conceives of menstruation only as the beginning of a 

 new sexual cycle because it is precipitated by degeneration of the corpus luteum. But 

 our concept also regards menstruation as a special interpolated event peculiar to man 

 and possibly to primates. It is a degenerative change. We would hence view it as 

 fallacious to compare menstrual bleeding with the pro-cestrous bleeding of the bitch 

 which comes from hyperemia and is a concomitant of growth, not degeneration. It 

 is equally fallacious to regard the oestrous vaginal desquamation of rodents as com- 

 parable to menstruation. This itself follows sudden growth changes in the vagina 

 precipitated by corpus decay and such growth changes are characteristic generally of 

 pro-oestrus and oestrus. Thus growth in the rat's mammary gland is inaugurated before 

 ovulation (Sutter). The simple conception that the vaginal lining as well as uterine 

 is protected by the corpus and degenerates on corpus impairment as Stockard and 

 Papanicolaou infer cannot be accepted. Nor can we follow these writers whose 

 work has otherwise marked so significant an advance in our knowledge of this subject 

 in their statement, "A secretion elaborated in the ovary apparently by the corpus 

 luteum is necessary for the normal development and persistence of the uterine and 

 vaginal mucosa." Only special growth changes (the oestrous and the pregravid changes, 

 or as we have termed them, pre-ovulatory and postovulatory ovarian effects) are refer- 

 able to the periodic function of the gonad not the actual existence of these mucous 

 membranes themselves. Their view of corpus luteum essentially would leave unex- 

 plained the actual growth and differentiation of the genitalia in the presence of the 

 prepubertal corpus-free gonad and also the integrity of the genitalia in animals which 

 have only one oestrous season per year and a very long time interval after corpus 

 decay; furthermore, such a view would not explain the first oestrous vaginal changes 

 in rats changes which could not result from a degeneration due to corpus decay for 

 no corpus has previously existed. 



