THE MAMMALIAN SEXUAL CYCLE 57 



menstruate periodically all the year round, they have a restricted 

 breeding season to which ovulation is confined, and observations 

 have been made relating to various species in the wild state and 

 pointing to the existence of such a season. There is evidence 

 also that for primitive man there was a restricted breeding season, 

 as Ploss, Westermarck, and others have shown, while the variation 

 in birth-rate in different countries, even in modern races, and 

 the occurrence of licentious feasts and sexual orgies and ceremonies 

 among the ancients, more particularly in the spring of the year, 

 afford further evidence of an increased disposition to sexuality 

 at definite recurrent intervals. The anthropological significance 

 of these ancient feasts, which are still represented in European 

 countries by the May Queen festivals and other similar customs, 

 and the intimate association between them and the idea of 

 reproduction, are fully discussed by Frazer in his book on " The 

 Golden Bough." 



Menstruation in women is accompanied by other periodic 

 phenomena besides those directly relating to the flow. During 

 pre-menstrual growth there may be a slight rise of temperature 

 and a quickening in the pulse-rate as well as other manifesta- 

 tions of an increased metabolism. There is a swelling of the 

 breasts, and frequently an enlargement of the thyroid, which 

 has been known occasionally to mark the commencement of a 

 goitre. With the actual flow these symptoms tend to subside, 

 but they may be continued until menstruation is over. The whole 

 period, as Head has pointed out, is one of diminution of control 

 by the central nervous system. This is apt to result in pain 

 which may extend to the whole body, there being a tendency 

 to react more vividly to any excitation capable of evoking dis- 

 comfort, and nervous depression is not uncommon. 



Of the existence of definite metabolic changes the evidence 

 is somewhat conflicting. Blair Bell states that there is a marked 

 fall in the calcium content of the blood, several investigators 

 (Schroder, Potthast, Murlin) have found a retention of nitrogen 

 at menstruation or during the prooestrum, but the cyclical varia- 

 tion is not the same for all individuals. 



It is a popular belief that women at the menstrual periods 

 are liable to contaminate food in handling it for cooking, etc., 

 owing to the emission from the skin of poisons or injurious 

 substances which taint anything that is touched. In support of 



