THE RHYTHM OF GONADAL FUNCTION" 591 



incidence of premature menses which can be produced by radiation or 

 ablation of the ovaries as due to the removal of the menstrual repression 

 exercised by the corpus. As long as the corpus is functional it continues 

 its specific "nourishment" of the endometrium; 19 and when it degenerates 

 or is injured or removed the latter structure must die. It is consequently, 

 as Meyer urges, no more correct to look upon the corpus as existing to 

 repress menstruation than to consider the conveyance of nourishment to a 

 living being as the repression of death instead of the conservation of life. 

 It is quite apparent why the uterine hemorrhage which occurs within two 

 or three days after extirpation or radiation of the ovary would normally 

 happen only after the operation had been done in the second half of the 

 menstrual cycle, as Seitz and Wintz have proven. Before that time the 

 functional or menstrual part of the endometrium has not been developed, 

 for this is dependent upon the function of the corpus luteum which has 

 not yet come into being or has barely been formed. 



Our present knowledge, on the other hand, firmly supports the con- 

 ception that functional corpora lutea do repress the further growth of 

 ovarian follicles and that their removal initiates a new cycle by permitting 

 follicular growth to take place. 20 



From the above considerations it is evident that no menstruation can 

 occur without a preceding ovulation and that the first menstrual blood flow 

 is incident upon the degeneration of the preceding and first corpus luteum 

 produced after the first ovulation. It is also clear why women in the 

 lactating period, or even after other amenorrheas due to ovarian hypo- 

 function, may conceive (and hence ovulate) without menstruating. Fur- 

 thermore, the old discussion as to whether in pregnancy the fertilized egg 

 belongs to the last normal or the first missed menstrual period was due 

 to the erroneous conception of the concurrence of ovulation and menstrua- 

 tion. Menstruation is always the terminal destruction of effects produced 

 by a preceding ovulation and its corpus luteum so that the fertilized ovum 

 belongs to the first missed menstruation, i. e., to the ovulation preceding it, 



19 This is elegantly shown by the fact that placentomata may be produced in the 

 rat's uterus (as Long and I have shown), during the time of lactation, when without 

 this special stimulus the uterus normally undergoes a "lactation atrophy." 



20 Stockard and Papanicolaou have thus hastened the occurrence of a new oestrous 

 cycle in the guinea pig by ablation of the corpora lutea. Most convincing and of great 

 scientific importance are the procedures of veterinarians, who by manual palpatory 

 methods express a persistent corpus luteum in cows which do not come in heat. The 

 artificially aroused oestrous is even said to appear in 50 per cent of all cases on the 

 evening of the third day or morning of the fourth and at all events in about 80 per cent 

 of the cases within the next four weeks. Zschokke and Hess especially have emphasized 

 the value of this operation, which is done both per rectum and per vaginam. It would 

 appear to have originated through the procedure of Zangger, who was the first to call 

 attention to cystic degeneration of ovaries in cattle failing to come in heat and first 

 practiced manual rupture of the ovarian cysts by way of the rectum. At about the 

 same time Zangger did his work Villiger introduced the enucleation of the corpus 

 luteum in the same way. Then Hegelund, Zschokke, Hess, Nielson, and Poulsen em- 

 ployed and expounded it for the induction of oestrus. The procedure is also used with 

 other aims, e.g., in retained desiccated fetus, pyometra, etc. 



