SEX IN" LIVING FORMS 125 



Menstruation is not peculiar to the human female, 

 being represented in the higher animals by what is 

 familiarly termed ''the rut." This is not usually a 

 bloody discharge, however, as in the human female, 

 though such a discharge has been observed in the 

 monkey. 



It has been quite satisfactorily settled that the dis- 

 charge of the ovum from the ovary generally takes 

 place about the time of the cessation of the flow. Im- 

 mediately after the discharge, the sexual desires of 

 the female are more intense than at other times. 

 This fact is particularly manifest in lower animals. 

 The following remark by Professor Dalton is espe- 

 cially significant to those who care to appreciate its 

 bearing : 



' ' It is a remarkable fact, in this connection, that the 

 female of these [domestic] animals will allow the ap- 

 proaches of the male only during and immediately after 

 the oestrual period [rut] ; that is, just when the egg is 

 recently discharged, and ready for impregnation. At 

 other times, when sexual intercourse would be necessa- 

 rily fruitless, the instinct of the animal leads her to 

 avoid it; and the concourse of the sexes is accordingly 

 made to correspond in time with the maturity of the 

 egg and its aptitude for fecundation." 



The amount of fluid lost during the menstrual flow 

 varies greatly with different individuals. It is esti- 

 mated at from three ounces to half a pint. In cases 

 of deranged function, it may be much greater than this. 

 It is not all blood, however, a considerable portion be- 

 ing mucus. It is rather difficult to understand why the 

 discharge of so considerable a quantity of blood is re- 

 quired. There is no benefit derived from a very copi- 

 ous discharge, as some suppose. Facts seem to indi- 



