88 THE PHYSIOLOGY OF REPRODUCTION 



VIII. Tin I!> <-ii i>,'i'<ii ion Stage. The changes which occur during 

 this stage are described by Heape as consisting of five processes, as 

 follows : 



(1) The re-formation of the epithelium. 



(2) The reduction of the blood supply. 



(3) The formation of new and recuperation of old 



blood-vessels. 



(4) The changes which take place in the stroma. 



(5) The behaviour of the leucocytes. 



(1) The new epithelium is formed, according to Heape, partly 

 from the epithelium of the glands, but partly from the underlying 

 stroma. The latter is described as a tissue of very primitive 

 characteristics, and the re-formation of the epithelium is regarded as 

 a specialisation of cells belonging to a layer which, in the embryo, 

 gave rise in the same way to similar epithelial cells (that is to say, 

 on this view, what takes place after menstruation is merely a 

 repetition of a process which occurs in the embryo). The new 

 epithelial cells, which are at first fiattened, gradually become cubical. 

 Heape's account is thus completely at variance with the descriptions 

 of those authors who hold that in the human female the epithelium 

 is renewed entirely from the torn edges of the old epithelium. 

 Heape states that the process of re-formation commences before the 

 expulsion of the menstrual clot, and even before the cessation of the 

 flow of blood into the uterine cavity. 



(2) There is still an escape of blood as long as the menstrual clot 

 lies within the uterine cavity, but after its expulsion the flow is 

 checked. Heape suggests that the contractions of the uterus which 

 serve to expel the clot may assist in stopping the escape of blood. 

 Probably, also, the growth of the new epithelium helps to stop the 

 ha-morrhage. After the growth of the new vessels the flow of blood 

 entirely ceases. 



(.'>) At the commencement of this stage many of the extravasated 

 blood corpuscles are seen lying in intercellular spaces in the stroma. 

 These corpuscles, according to Heape, are drawn again into the 

 circulatory system by becoming enclosed within newly formed 

 capillaries. Heape describes the process as follows: " The protoplasm 

 of the cells bounding these [blood-containing] spaces flattens out, the 

 nuclei of the cells becoming also flattened and elongated, and 

 numerous fine capillary vessels are thus formed, continuous with the 

 deeper parts of the mucosa with large pre-existing capillaries, and so 

 with the circulatory system. 



"These fine capillaries exist only temporarily. When the blood 

 corpuscles are again drawn into the circulation, and when the mucosa 



