REPRODUCTION IN MAN 1277 



lost at each, menstrual period varies between 100 and 300 grm. During the 

 ' period ' there are often disturbances of other functions of the body, which 

 are so common that to be ' unwell ' is the recognised polite description of 

 the menstrual period. Thus it is often attended with pains in the abdomen, 

 a feeling of weight and fulness, disturbance of digestion, headache, and 

 neuralgias of various distribution. At the same time there is a general 

 disinclination for exertion. 



Menstruation is due to periodic changes in the uterine mucous membrane. 

 During the few days previous to the period the mucous membrane undergoes 

 a rapid hypertrophy, increasing in thickness from 2 mm. to 6 mm. At the 

 same time there is increased vascularity of the membrane in consequence of 

 dilatation of its blood vessels. At the commencement of the menstrual 

 period there is an escape of the red blood corpuscles, chiefly by diapedesis, 

 but partly by actual rupture of the blood capillaries into the spaces between 

 the uterine glands. At this period sections of the uterine mucous mem- 

 brane show numerous collections of red blood corpuscles, lying immediately 

 under the superficial epithelium. In some cases this stage is followed by 

 an almost complete desquamation of the superficial epithelium. Generally 

 the desquamation is only partial, but in either case the blood escapes into 

 the cavity of the uterus, where it becomes mixed with the increased secre- 

 tion from the uterine glands and is discharged into and from the vagina as 

 the menstrual fluid. With the occurrence of the menstrual flow the mucous 

 membrane begins to diminish in thickness. The vascularity decreases, and 

 much of the blood in the deeper parts of the mucosa becomes reabsorbed. 

 The desquamated epithelium is replaced by proliferation of the cells which 

 remain intact, so that finally the mucosa is completely regenerated and 

 brought back to its original condition. This period of regeneration lasts 

 about fourteen days. During the next few days the condition of the mem- 

 brane is stationary, but this period of rest lasts but a short time, since signs 

 of the pre-menstrual swelling can be detected as early as three days before 

 the onset of the next menstrual period. 



. THE RELATION OF OVULATION TO MENSTRUATION 



There is no doubt that menstruation depends on the functional activity 

 of the ovary. Its onset coincides with the first production of ripe ova in the 

 ovary, and it ceases with the cessation of ovulation at the climacteric or 

 menopause. In cases where the ovaries have been removed before puberty 

 menstruation never occurs. Removal of both ovaries during adult life 

 generally brings about a premature menopause. It seems probable that 

 the ripening of the ova in the human ovary occurs at periods corresponding 

 to those of menstruation. But there has been much division of opinion as to 

 the exact relation between the two processes. Fairly definite clinical and 

 post-mortem evidence has been brought forward for the theory that ovula- 

 tion precedes the menstrual flow. On this theory the degeneration of 

 the uterine mucous membrane, which occurs at each period, represents, so 



