178 PHYSIOLOGY CHAP. 



is mostly in the form of detritus, but occasionally especially in 

 virgins there has been observed detachment of the epithelium 

 in coherent form as a fine membrane to which is given the name 

 of catamenial decidua. With the post-haemorrhagic detachment 

 of the epithelium just described harmonises the fact that the 

 menstrual flow during the first three days presents the colour 

 of venous blood, and in the days following always becomes paler 

 and less in quantity. 



The amount of blood which, is lost during menstruation differs 

 much in each individual (from 100 to 300 or from 30 to 40 

 grms.), and is naturally in proportion to the extent and in- 

 tensity of the bleeding from the mucosa, and the consequent 

 degeneration and detachment of tissue. The haemorrhage is 

 confined to the mucosa of the body of the uterus ; the oviduct, 

 the cervix of the uterus, and the external genitals do not par- 

 ticipate in the process, except by a slight increase in the 

 secretion of mucus. 



After the haemorrhagic and degenerative stage follows the 

 stage of regeneration of the uterine mucous membrane. The 

 remaining infiltrated blood is reabsorbed; the exfoliated epi- 

 thelium renews itself by karyokinesis, and after about fourteen 

 days from the beginning of the menstrual flow the mucosa is 

 restored to its normal condition. 



If one takes into account the fact that menstruation recurs 

 normally every twenty-eight days, and is preceded by the stage of 

 tumefaction of the mucosa which lasts from four to five days, it 

 may be concluded that the resting period of the uterine mucosa 

 which intervenes between two successive menstruations is not more 

 than ten days. From what has been said it is easy to foresee 

 that the menstrual flow cannot be constituted of pure blood, 

 but of blood mixed with mucus and more or less degenerate cells 

 of the uterine and vaginal epithelium, which in fact are observed 

 and recognised easily with the microscope, together with ery- 

 throcytes and leucocytes. Menstrual blood, on account of the 

 alkaline mucus with which it is mixed, does not readily coagulate, 

 and has a more or less unpleasant odour, not adapted certainly 

 to promote venereal excitement, but rather to depress it. It 

 may even prove irritant to the mucosa of the glans penis and 

 male urethra, independently of the eventual virulent action of 

 gonococci. However, the opinion largely diffused among the 

 lay public, that menstrual blood has poisonous properties trans- 

 missible to the male, is certainly exaggerated. This belief takes 

 its origin from the old theory which considered menstruation 

 as a purification by which the woman each month purged herself 

 of certain poisonous materials accumulated in the blood. From 

 that theory also come the name of purgatio mensile given to 

 menstruation and the precept imposed by the Rabbis on the 



