THE HORMONES IN HUMAN REPRODUCTION 



or two next month and perhaps completely out of phase next 

 season. I once had 4 females of the Java monkey (Macaca 

 irus) in a cage adjacent to a large group of the closely related 

 Rhesus monkeys. While the latter were running cycles of 28 

 days' modal length, their Javanese cousins, living under the 

 same moon, were exhibiting a modal cycle length of 35 days. 

 As mentioned in Chapter III, the cycles of other mammals 

 may vary from 5 days to a year in length, and if we consider 

 the birds and insects we finds cycles of one day to 17 years. 

 If the heavenly bodies are to control these rhythms, the cycle 

 of the 17-year locust calls for a hitherto unknown comet ! 



The idea of a relation between human menstruation and 

 the moon is, however, ancient and widespread. It was, no 

 doubt, suggested by the obvious and inescapable relation 

 between the moon and the tides of the sea. If the moon can 

 control the ebb and flow of great waters, why not also the 

 tides of human life .'' Perhaps the popular mind has also been 

 influenced by the fact that outbursts of insanity in women 

 sometimes accompany the menstrual cycle ; this seems again 

 to link menstruation with the moon, which has long been con- 

 sidered a cause of lunacy. Then there are, of course, certain 

 special cases in nature in which the life of an animal is directly 

 influenced by the moon or the tides (e.g. the palolo. Chapter 

 III) . These cases may have helped to foster the notion we are 

 discussing. As lately as 1898 the eminent Swedish physicist 

 Svante Arrhenius thought he had proved the connection of 

 lunar and menstrual cycles by mathematical evidence, but 

 this has been completely disproved, notably by the English 

 physicians Gunn, Jenkin, and Gunn (1937). It is indeed diffi- 

 cult to conceive of any direct participation of the moon in the 

 reproductive cycles of the land-dwelling primates, for if it 

 were really efl*ective we should expect menstruation to occur 

 at the same phase of the moon in all females of a given species, 

 a state of aff"airs that would have made the social organiza- 

 tion of mankind unthinkably different from what it is. 



{ 138 } 



