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February 22, 1941


Author Affiliations

From the Department of Anatomy, University of Chicago.

JAMA. 1941;116(8):702-704. doi:10.1001/jama.1941.62820080003010

In the human species, menstruation is the only overt manifestation of rhythm in the female reproductive system. In other primates there may be additional and even more obvious indications of cyclic changes. Corner1d and Edgar Allen1e have recently summarized the evidence that the rhythm is maintained by a delicate balance of endocrines. We are not dealing with "an all or none" phenomenon but with a balanced system of forces which changes as a whole when any one factor changes. The oscillations of the system may have a high amplitude or they may become almost imperceptible. The system is accordingly variable in its manifestations. This is generally conceded; the difference of opinion is largely a matter of the range of variability that is to be regarded as normal. Many clinicians are unwilling to regard a cycle as normal unless its primary purpose is achieved; i. e., unless a fertilizable