604 REPRODUCTION. 



when sexual intercourse would be fruitless, the instinct of the animal 

 leads her to avoid it ; and the concourse of the sexes accordingly cor- 

 responds in time with the maturity of the egg and its aptitude for 

 fecundation. 



Menstruation. 



In the human female, the periodical excitement of the generative 

 apparatus is marked by a group of phenomena known as menstruation, 

 which are of sufficient importance to be described by themselves. 



During infancy and childhood the sexual system is inactive. No 

 eggs are discharged from the ovaries, and no external phenomena show 

 themselves, connected with the reproductive function. 



But at the age of fourteen or fifteen years, a change becomes visible. 

 The outlines of the body grow more rounded, the breasts increase in 

 size, and the entire aspect undergoes a peculiar alteration, dependant on 

 the approach of maturity. At the same time a discharge of blood takes 

 place from the generative passages, accompanied by some disturbance 

 of the general system, and the female is then known to have arrived 

 at the period of puberty. 



Afterward, the discharges recur at intervals of four weeks ; and, from 

 their correspondence in time with successive lunar months, they are 

 designated as the "menses" or "menstrual periods." These periods 

 are usually regular in recurrence, from their first appearance, until about 

 the age of forty-five years. During this time the female is capable of 

 bearing children, and sexual intercourse is liable to be followed by 

 pregnancy. After the forty-fifth year, the periods first become irreg- 

 ular, and then cease ; their final disappearance being an indication that 

 pregnancy cannot again take place. 



Between the ages of fifteen and forty-five years, the regularity of 

 the menstrual periods indicates to a great extent the individual apti- 

 tude for impregnation. All causes of ill health which derange men- 

 struation are also apt to interfere with pregnancy ; and women whose 

 menses are regular are more likely to become pregnant, after sexual 

 intercourse, than those in whom the periods are absent or irregular. 



When pregnancy takes place, however, the menses are suspended 

 during its continuance. They usually remain absent, after delivery, 

 until the end of lactation, when they recommence, and recur at regular 

 intervals, as before. 



When the menstrual period is about to come on, the female is usually 

 affected with some degree of discomfort and lassitude, a sense of weight 

 in the pelvis, and a more or less disinclination to society. These symp- 

 toms are in some instances slightly pronounced, in others more distinct. 

 A discharge of vaginal mucus then begins to take place, soon becoming 

 yellowish or rusty-brown in color, from the admixture of blood ; and 

 by the second or third day it has the appearance of nearly pure blood. 

 The unpleasant sensations, at first manifest, then usually subside ; and 

 the discharge, after continuing for two or three days longer, grows 

 more scanty. Its red color diminishes in intensity, becoming brown- 



