MENSTRUATION. 305 



to Longet, this estimate is rather low, the quantity ordinarily 

 ranging from ten to twelves ounces, occasionally amounting 

 to seventeen ounces, or even more. 1 It is well known that 

 the quantity is exceedingly variable, as is the duration of the 

 flow, and the difficulties in the way of collecting and estima- 

 ting the total discharge are evident. 



The characters of the menstrual flow are sufficiently sim- 

 ple. Supposing the discharge to continue for four days, on the 

 first day, the quantity is comparatively small ; on the second 

 and third, the flow is at its height ; and the quantity is dimin- 

 ished on the fourth day. During this stage, the fluid has the 

 appearance of pure arterial blood, not coagulated, and mixed, 

 as has been shown by microscopical examination, with pave- 

 ment-epithelium from the vagina, cylindrical cells from the 

 uterus, leucocytes, and a certain amount of sero-mucous se- 

 cretion. Chemical examination of the fluid does not show 

 any marked peculiarities, except that the quantity of fibrin is 

 either not estimated or is given as much less than in ordinary 

 blood. 2 



The mechanism of the haemorrhage, which will be con- 

 sidered more fully when we come to study the changes in 

 the uterine mucous membrane during menstruation, is prob- 

 ably the same as in epistaxis. There is a rupture of small 

 blood-vessels, probably capillaries, and blood is thus ex- 

 uded from the entire surface of the membrane lining the 

 uterus, and sometimes from the membrane of the Fallopian 

 tubes. The blood is then discharged into the vagina and is 

 kept fluid by the vaginal mucus. The mucus of the body of 

 the uterus is viscid and alkaline ; the mucus secreted at the 

 neck is gelatinous, viscid, tenacious, and also alkaline ; the 



1 LONGET, Trait'e de physiologie, Paris, 1869, tome iii., p. 772. 



9 Several analyses of the menstrual fluid, taken from the older writers, 

 are given by Simon. (Animal Chemistry, Philadelphia, 1846, p. 274.) Accord- 

 ing to more recent observations, the menstrual blood is only apparently deficient 

 in fibrin, because coagulation is prevented by admixture with vaginal mucus. 

 (GORUP-BESANEZ, Lehrbuch der physiologischen Chemie, Braunschweig, 1862, S. 

 333.) 



