CHAPTER III 



THE OVARY AS TIMEPIECE 



OUR western plainsmen used to watch, in August 

 I and September, milling herds of bison, blackening 

 the prairie for miles. It was no uncommon thing to 

 see thousands of them, eddying and wheeling about under a 

 dense cloud of dust raised by the bulls as they pawed in the 

 dirt or engaged in desperate combat. In these herds the males 

 were continually following the females and mating with them. 

 The whole mass was in constant motion, all bellowing at once 

 in deep and hollow sounds, which mingling together seemed 

 at the distance of a mile or two like the noise of distant thun- 

 der.^ This was the yearly period of estrus,^ the mating time, 

 when the females were ready to produce their eggs, and the 



1 This passage is largely a quotation from George Catlin, The North 

 American Indians, vol. 1 (p. 280 in the Edinburgh reprint of 1926). 

 Catlin's rather discreet painting of such a scene occurs in the same 

 volume, fig. 105. 



2 Estrus is the technical term for recurrent periods of sexual excite- 

 ment in animals, popularly called "heat." It was introduced in 1901 by 

 Walter Heape, a prominent student of the physiology of reproduction. 

 The word comes from the insect described by Virgil: 



"About the groves of Silarus and Alburnus evergreen 

 In holm-oak swarms an insect 



We call the gadfly ('oestrus' is the Greek name for it) — 

 A brute with a shrill buzz that drives whole herds crazy 

 Scattering through the woods, till sky and woods and the banks of 

 Bone-dry rivers are stunned and go mad with their bellowing." 



{Georgics, Book III, C. Day Lewis's translation.) 

 In its Latin neuter form oestrum this word long ago became an English 

 word meaning any recurrent excitement, e.g. the poetic frenzy. Heape 

 adopted the masculine form as his special technical term. In England 

 it is spelled oestrus and the first syllable is pronounced e as in "me." In 

 the United States, following a general trend of our language, it is now 

 commonly spelled estrus and pronounced with e as in "west." The 

 adjectival form is estrous; cf. mucus, m,ucous. The interval between two 

 estrous periods, in Heape's terminology, is diestrus; a long period be- 

 tween sexual seasons (as for example in sheep during the winter) is 

 anettrus. 



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