570 OVULATION AND FUNCTION OF MENSTRUATION. 



to the skin of the buttocks, the thighs, and the under part of the 

 tail. 1 



The system at large is also visibly affected by the process going 

 on in the ovary. In the cow, for example, the approach of an 

 oestrual period is marked by an unusual restlessness and agitation, 

 easily recognized by an ordinary observer. The animal partially 

 loses her appetite. She frequently stops browsing, looks about un- 

 easily, perhaps runs from one side of the field to the other, and then 

 recommences feeding, to be disturbed again in a similar manner 

 after a short interval. Her motions are rapid and nervous, and her 

 hide often rough and disordered ; and the whole aspect of the ani- 

 mal indicates the presence of some unusual excitement. After this 

 condition is fully established, the vaginal secretions show them- 

 selves in unusual abundance, and so continue for one or two days ; 

 after which the symptoms, both local and general, subside sponta- 

 neously, and the animal returns to her usual condition. 



It is a remarkable fact, in this connection, that the female of 

 these animals will allow the approaches of the male only during and 

 immediately after the oestrual period ; that is, just when the egg is 

 recently discharged, and ready for impregnation. At other times, 

 when sexual intercourse would be necessarily 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. 



II. MENSTRUATION. 



In the human female, the return of the period of ovulation is 

 marked by a peculiar group of phenomena which are known as 

 menstruation, and which are of sufficient importance to be described 

 by themselves. 



During infancy and childhood the sexual system, as we have 

 mentioned above, is inactive. No discharge of eggs takes place 

 from the ovaries, and no external phenomena show themselves, 

 connected with the reproductive function. 



At the age of fourteen or fifteen years, however, a change begins 

 to manifest itself. The limbs become rounder, the breasts increase 

 in size, and the entire aspect undergoes a peculiar alteration, which 

 indicates the approaching condition of maturity. At the same 

 time a discharge of blood takes place from the generative passages, 



1 Ponchet, Theorie positive de 1'ovulation, &c. Paris. 1847, p. 230. 



