THE EHYTHM OF GONADAL FUNCTION 589 



vigorous and extensive growth. It would appear that these growth changes 

 are due to the liberation of hormones from the ovary, since much growth 

 does not take place on ablation of the ovaries or in conditions of hypo- 

 ovarism. As far as we know, the most active ovarian tissue at this time 

 in the cycle is represented by the growing follicles. These, as we have 

 seen, are in the other mammalia also associated with certain growth 

 changes in the reproductive tube during the periods of pre-oestrus, osstrus 

 and postoestrus. 16 Ovulation and the production of the corpus luteum 

 can also be said to exert a specific effect upon the endometrium for corpus 

 hormones would seem definitely responsible not merely for the further 

 growth of the endometrium to its premenstrual height but also for the 

 assumption of the function of secretion on the part of the uterine glands. 

 We have already said that Schroeder has discovered this to be evident as 

 early as the thirteenth day, so that the correspondence with ovulation is 

 quite close. 17 



The so-called premenstrual endometrium, therefore, while with char- 

 acteristics more pronounced near the end of the menstrual period, is 

 nevertheless the resultant of a gradual transformation which has been 

 taking place from the moment when the corpus luteum was produced in 

 the ovary through follicular rupture, and it may rightly be regarded as a 

 product of the activity of that ovarian structure. Furthermore, the recent 

 work of Marcotty, Miller and E. Meyer has shown a beginning fatty de- 

 generation of the corpus of the preceding ovulation in man at the time of 

 onset of menstruation. A new, and it would appear a sound, interpreta- 

 tion of menstruation is furnished by these facts. Menstruation may be 

 regarded as the degeneration of uterine tissue which has been built up 

 and specifically nourished by hormones from the corpus luteum, hormones 

 which have been suddenly withdrawn on the degeneration of the corpus. 

 In other mammalia (e. g., the rabbit) we have seen that rather extensive 

 uterine changes are also produced by the corpus, but in these cases it 

 would appear that on the death of the corpus or diminution of its activity 

 there is a slower and gradual resorption of the accessory uterine tissues. 

 Apparently only in man and the primates is this uterine degeneration 

 "stormy," i. e., so sudden that an extensive wound is produced which must 



18 It is true that Marshall and Runcimann have challenged the specific idea that 

 hormones from the expanding follicles are responsible for bringing on heat, for their 

 premature rupture of these follicles and consequent artificial production of corpora 

 lutea in bitches at a time preceding an expected oestrus did not delay the latter. 

 Their results are open to criticism. Proof that all of the follicles in question were 

 found and ruptured is difficult or impossible to deduce. Sonnenberg (see also Marshall 

 (6), Phil. Trans., 1903, B 196 and Marshall and Jolly, same, B 198) has reported the 

 artificial production of heat in animals by the subcutaneous injection of the liquor 

 folliculi from other animals which were in heat. 



17 It is in fact probable that the corpus luteum must be several days old in order 

 to exert this effect and it is probable that in my diagram ovulation should be shifted 

 still further forward and in front of Schroeder's calculations to a greater extent 

 than I have done; possibly the ninth or tenth day of the cycle would have been 

 preferable. 



