588 HERBEET M. EVANS 



only by the assumption that it is constantly related to the cohabitation act, 

 that it is in fact almost coincident with it. The method of study of the 

 degree of development of young embryos is therefore well calculated to 

 disclose whether a standard or variable time of ovulation can be said to 

 exist. Grosser, Triepel, Mall and Zangemeister have examined with this 

 special point in view all early human embryos where the time of cohabita- 

 tion was supposedly known. Unfortunately, the data are fragmentary 

 and inharmonious. Such as the evidence is, however, it tends to stress 

 one of the points established by the study of war pregnancies, that is, that 

 ovulation can occur on almost any day of the menstrual cycle. Only five 

 or six cases of undoubtedly reliable history probably exist and it is obvious 

 that these are too few for us to parallel with the data on the "conception 

 optimum." We may expect that sufficient and unimpeachable data will 

 eventually enable us to substantiate the statement made by Mall, who felt 

 that the embryological data even now support and will support the "con- 

 ception optimum" data on ovulation being usually early in the inter- 

 menstruum and thus will furnish another check on our notion that this 

 is the normal time of ovulation as we have seen by direct study of the 

 ovary. 15 



C. Chronological Relations of Menstruation and Ovulation and Com- 

 parison of Uie Menstrual and (Estrous Cycle. We may thus regard the 

 researches upon human ovulation as tending more and more convincingly 

 to show this act to take place normally somewhat before the middle of the 

 menstrual cycle (the menstrual cycle being regarded as the complete time 

 interval from the first appearance of one menstrual hemorrhage to the 

 next). In Fig. 1 the time of ovulation is thus approximately or dia- 

 grammatically placed. The newer studies on the uterine mucosa and the 

 chronological relations between the time of ovulation and menstruation 

 now enable us to have a more intelligible conception of the interrelation 

 of uterus and ovary in man, an interrelation which we have already seen 

 to be fundamental in the other mammalia. During the preovulatory 

 phase of the menstrual cycle the lining of the uterus, which has been almost 

 denuded by menstruation, does not merely repair itself but undertakes 



15 As to the quandary in which we are placed by the recognition of irregular, i.e. 

 very early or very late, ovulation, two attempts at explanation have been made. Robert 

 Meyer claims that the exact time of follicular rupture is indeed open to considerable 

 variation but that the maturation of the ovum and lutein change of the granulosa 

 cells is less variable. The proof of this contention is not yet at hand. Triepel has 

 advanced the idea that, though a normal time for spontaneous ovulation exists, coitus 

 may precipitate this or induce another ovulation. Were this true, infertile coitus 

 should thus greatly disturb the menstrual rhythm and it does not do so. Furthermore, 

 TriepoPs hypothesis, as he admits, calls for the presence of large follicles or other 

 favorable ovarian conditions at any time in the cycle. The variation in the time of 

 ovulation, while apparently proven, is thus difficult to explain and perhaps can only 

 be harmonized with the growing body of evidence which points to a standard time of 

 ovulation by the view that most of such variations occur in single coitus pregnancies, 

 where a condition of relative sexual abstinence might be conceived as favoring the idea 

 of an unusual response the induction of ovulation as a cohabitation effect. 



