1370 PHYSIOLOGY 



which are typical of the sex. The amount of blood lost at each men- 

 strual 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 membrane 

 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 secretion from the uterine glands and is discharged 

 into and from the vagina as the menstrual fluid. With the occur- 

 rence 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 menstrua- 



