THE (ESTROUS CYCLE IN THE MAMMALIA 67 



known to occur. 1 The voice also is liable to be affected at the 

 menstrual periods, and the skin and breath sometimes have a 

 peculiar odour. Mental depression may exist, and be accom- 

 panied by nervous pathological phenomena. 



According to the upholders of the " Wellenbewegung " 

 hypothesis 2 the reproductive life of the human female consists 

 of a succession of wave-like periods which follow the monthly 

 cycle. Thus, according to Stevenson, 3 the curve of temperature 



FIG 1. Diagram illustrating the "Wellenbewegung" hypothesis. The 

 curve AB represents the varying intensity of the vital processes during 

 the twenty-eight days of the menstrual cycle. The numbers between 

 m and n represent the days occupied by menstruation. (From Sellheim.) 



is above the mean line for about half the month, when it rises 

 to half a degree above the mean. It falls below the mean line 

 just before the onset of menstruation, during which it remains 

 about half a degree below. Similar results were obtained by 



1 See p. 350, Chapter IX. 



2 Godman, "The Cyclical Theory of Menstruation," Amer. Jour. Obstet., 

 vol. xi , 1878. Reinl, " Die Wellenbewegung des Lebensprozesses des Weibes," 

 Volkmann's Sammlung klin. Vortrage, No. 273. Ott, " Les lois de la periodicity 

 de la fonction physiologique dans 1'organisme feminine," Nouvelles Arch, 

 d' Obstet. et de Gijnec., 1890. 



3 Stevenson, "On the Menstrual Wave," Amer. Jour. Obstet., vol. xv., 1882. 



