158 THE PHYSIOLOGY OF REPRODUCTION 



of prooestrous destruction, may serve to provide a rich pabulum on 

 which to nourish the embryo during the earliest days of pregnancy. 



In opposition to these theories it may be urged that pregnancy 

 has been known to take place in women who have never menstruated, 

 and that it may occur during periods of amenorrhcea, or during the 

 lactation period, when menstruation is sometimes in abeyance.- Such 

 cases, however, are the exception, and it must not be inferred that, 

 because the prooestrous function can occasionally be dispensed with 

 without inducing a condition of sterility, it normally plays no part 

 in the physiology of generation. 



It has been pointed out, however, that the severity of the 

 menstrual process in woman is occasionally so great as to be 

 positively injurious, and that such cases evidently belong to the 

 category of constitutional disharmonies which Metchnikoff^ has 

 shown to be so common in the organs and functions of the generative 

 system. 



Geddes and Thomson ^ also have called attention to the patho- 

 logical character of menstruation, as evidenced not only by the pain 

 which frequently accompanies the process, and the local and con- 

 stitutional disorders by which it is often attended, but by the general 

 systemic disturbance which always occurs synchronously with it. 

 These authors interpret the discharge as a means of disposing of 

 the anabolic surplus which is consumed during pregnancy by the 

 developing embryo. A similar view is adopted by Webster,* who 

 associates the introduction of menstruation (as distinguished from 

 the procBstrum of the lower animals) with a diminished fertility. 



Reference has already been made to the " Wellenbewegung " or 

 " wave" hypothesis regarding the nature of menstruation (see p. 61).* 



The physiological cause of the prooestrum, and the probable part 

 played by the ovaries in this connection, will be discussed at some 

 length in a later chapter. 



' Metchnikoff, The Nature of Man, London, 1903. 



^ Geddes and Thomson, The Evolution of Sex, Revised Edition, London, 1901. 



^ Webster, " The Biological Basis of Menstruation," Montreal Med. Jour., 

 April 1897. 



* The cyclical changes in the size of the ovaries are referred to on pp. 22 and 

 53 (footnote). 



