THE MENSTRUAL CYCLE 



finally ovulation. This theory, and one or two ingenious varia- 

 tions upon the same theme by later English writers, F. H. A. 

 Marshall and Zuckerman, all seem too complex to be probable, 

 and moreover they suffer from a very serious objection. 

 Unlike the menstruation-like bleeding, which can be produced 

 in monkeys and women by withdrawing estrogenic hormone, 

 the proestrous bleeding of dogs is produced by building up 

 the level of estrogenic hormone, as was shown by R. K. Meyer 

 and Seiichi Saiki in our Rochester laboratory in 1931. 



A few years ago, Carl G. Hartman discovered that in 

 Rhesus monkeys there is almost always a slight bleeding from 

 the uterus about the time of ovulation. This does not show 

 externally and is discernible only by applying the microscope 

 to washings of the vagina. Sections of the uterus made at 

 this time reveal that a few red blood cells are escaping from 

 superficial capillary blood vessels of the endometrium, which 

 are engorged by the action of the estrogenic hormone. In the 

 laboratories we call this slight bleeding "Hartman's sign" 

 and take it as evidence that there is a ripe follicle in the ovary. 

 This is the actual equivalent of Heape's proestrous bleeding. 

 It has since been found to occur in women, though probably 

 not as regularly as in monkeys. These observations prove 

 clearly that menstruation is something else than proestrous 

 bleeding. 



Hartman has proposed another explanation for menstrua- 

 tion. He points to the fact that in many mammals, at the 

 time of implantation of the embryo, the uterine secretion con- 

 tains red blood cells. He tells us also that in many viviparous 

 animals lower than the mammals, for example certain sala- 

 manders and fish, in which the embryo depends upon the 

 maternal tissues for nourishment, bleeding in one form or 

 another usually occurs into the brood chamber. Hartman 

 compares menstruation to bleeding of this kind and conjec- 

 tures that it is simply a means of getting the vitally useful 

 blood pigment, hemoglobin, into the region where the early 



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