52 INTRODUCTION TO SEXUAL PHYSIOLOGY 



extravasated in tlie tissue. It .subsequently forms large lacuna- 

 like spaces in the superficial part of the tissue, and then the 

 epithelium ruptures and bleeding takes place in the cavity. 

 The whole, or a great part of the superficial epithelium, is removed 

 as a result of the extensive hsemorrhage, and a varying amount 

 of underlying stroma tissue may also be torn away, leaving the 

 lumen of the uterus bounded by a raw edge. The discharged 

 blood, together with degenerate epithelial and stroma cells, 



Fk;. 'Id. — Section through mucosa of human uterus, showing 

 pre-nienstrual congestion. (From Sellheim.) 



constitute the menstrual clot, and this along with a sanguine - 

 mucous flow passes down the uterus and through the vagina 

 to the exterior. The amount of blood lost in a Avoman is on an 

 average about three ounces, and the discharge lasts from three 

 to six days. The uterine glands are active during menstruation 

 and contribute to the discharge. When the tissue denudation is 

 exceptionally great the condition is known as ynenorrhagia, and 

 when it results in a painful condition it is called dysmenorrhoea. 



During the next period, repair sets in, the epithelium being 

 renewed either from cells which did not suiler destruction in 



