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HAND-BOOK OF PHYSIOLOGY. 



Characters of Menstrual Discharge. The menstrual discharge is 

 a thin sanguineous fluid, having a peculiar odor. It is of a dark color, 

 and consists of blood, epithelium, and mucus from the uterus and vagina, 

 serum, and the debris of a membrane called the decidua menstrualis. 

 This membrane is the developed mucous surface of the body of the 

 uterus. It does not extend into the Fallopian tube or into the cavity of 

 the cervix. It attains its highest state of development in the unimpreg- 

 nated organ just before the commencement of a catamenial flow (Fig. 396). 

 If impregnation take place, it becomes the decidua veraj if impregnation 



FIG. 396. 



FIG. 397. 



FIG. 398. 



FIG. 396. Diagram of uterus just before menstruation; the shaded portion represents the thick- 

 ened mucous membrane. 



FIG. 397. Diagram of uterus when menstruation has just ceased, showing the cavity of the 

 uterus deprived of mucous membrane. 



FIG. 398. Diagram of uterus a week after the menstrual flux has ceased: the shaded portion 

 represents renewed mucous membrane. (J. Williams.) 



fail, the membrane undergoes rapid disintegration; its vessels are laid 

 open and haemorrhage follows (John Williams). The blood poured out 

 does not coagulate in consequence partly of the admixture already men- 

 tioned, or, very possibly, coagulation occurs, but the process is more or 

 less spoiled, and what clot is formed is broken down again, so as to imi- 

 tate liquid blood. (See also p. 73, Vol. I.) 



Menstruation, therefore, is not the result of congestion, or of a species 

 of erection, but of a destructive process by which the decidua or nidus 

 prepared for an impregnated ovum is carried away. It is not a sign of the 

 capability of being impregnated as much as of disappointed impregnation. 



The occurrence of a menstrual discharge is one of the most prominent 



