THE CESTROUS CYCLE IN THE MAMMALIA 61 



formation of pigment, are also 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 accompanied by nervous pathological phenomena. 



Many women are more excitable before the onset of menstruation 

 and others during the process. With the onset the pulse-rate, blood 

 pressure, and temperature generally rise. The bacterial resistance 

 of the subject is reduced. After menstruation there is a period of 

 slackness, sometimes associated with headache and depression. 



As Head has pointed out, the general bodily state at the menstrual 

 periods forms a potent cause of diminished automatic control by 

 the central nervous system. "This physiological act may be 

 accompanied by referred pain, confined strictly to those segments 

 which stand in direct relation with the pelvic organs, or the morbid 

 sensations may occupy the whole of the body and lower extremities 

 below the level of the umbilicus, with or without the cervical areas 

 and occipital region of the scalp. Finally, the head, trunk, and even 

 the limbs may become painful and tender in parts that have no 

 direct relation to stimuli within the pelvic organs. The extent to 

 which such widespread generalisation occurs, depends more on the 

 temperamental condition of the patient than on the intensity of the 

 painful irritation." 2 This diffusion of painful sensation is due to 

 diminished central resistance ; potentially painful impulses which 

 would normally have been inhibited or strictly confined to areas 

 appropriate to the organ affected are allowed to spread widely. 

 There is a tendency during menstruation to react more vividly to 

 any excitation capable of evoking discomfort. 



Painful menstruation, when so pronounced as to be considered 

 pathological, is called dysmenorrhoea ; diffuse or protracted menstrua- 

 tion is termed menorrhagia; but there are all gradations between 

 these conditions and normality. 3 



According to the upholders of the " Wellenbewegung " hypothesis 4 

 the reproductive life of the human female consists of a succession of 

 wave-like periods which follow the monthly cycle. Thus, according 

 to Stevenson, 5 the curve of temperature is above the mean line for 



1 See p. 384, Chapter IX. 



2 Head, "The Release of Function in the Nervous System," Croonian 

 Lecture, Proc. Roy. <S'oc., B., vol. xcii., 1921. 



:! For amenorrhoea, see pp. 60 and 69. 



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

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

 Volkmann's Sammlung liin. Vortrage, No. 273. Ott, "Les lois de la periodicite 

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

 cPObstet. et de Gyne'c., 1890. See also Havelock Ellis, Nan and Woman : a Study 

 of Human Secondary Sexual Characters, 5th Edition, London, 1914. This work 

 contains a fund of valuable information. 



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



