458 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



laries into the connective-tissue spaces beneath the epithelial lining of the 

 uterine wall. The epithelium is thus pressed up from beneath, and begins 

 rapidly to undergo fatty degeneration in places, and to disappear. The 

 immediate cause of the degeneration is nut definitely known. The connective- 

 tissue elements and the upper portion of the glands are involved to some extent 

 in the degenerative change. The capillaries, thus laid bare, burst, and the dark 

 blood oozes forth and, mixed with disintegrated remains of the uterine tissues, 

 with the mucous secretion of the uterus and the vagina, and with the escaped 

 lymph, passes away, drop by drop, from the body. There is great difference of 

 opinion as to the extent of the destruction of uterine tissue. On the one extreme 

 side are those who claim that the loss of tissue is normally wholly trivial and 

 secondary, the hyperemia and the bloody glandular discharge being the 

 important events. Other authorities, equally extreme, have observed a disap- 

 pearance of the whole mucous membrane except the deepest layers containing 

 the bases of the glands ; this is probably pathological. From all the evidence an 

 opinion inclining toward the former view seems most reasonable — namely, 

 that usually and physiologically only the superficial portion of the mucous 

 membrane disintegrates, and this only in spots. 1 Differences in the amount 

 undoubtedly occur. Occasionally it happens that the membrane, instead of 

 disintegrating, comes away in pieces of considerable size. The term deddua 

 nwnstrualis is applied to the lost coat. The flow continues upon an average 

 four days or more. From observations upon 2080 American women Emmet 2 

 finds the average duration of the flow at puberty to be 4.82 days, the average 

 in later life 4.66 days. The amount of blood discharged can be determined 

 only with great difficulty. It probably varies greatly, but is commonly 

 estimated at from 100 to 200 cubic centimeters (4 to 5 ounces). The blood is 

 slimy, with abundant mucus; usually it does not coagulate. Epithelium 

 cells, red corpuscles, leucocytes, and detritus from the disintegrated tissues, 

 occur in it. and it lias a characteristic odor. As the flow ceases a new growth 

 of connective-tissue cells, capillaries, glands, and from the glands superficial 

 epithelium, begins, and the mucous membrane is restored to its original 

 amount. Whether a resting period follows before the succeeding tumefaction 

 occurs is not definitely known, but it seems probable. The durations of the 

 various steps in the uterine changes are not well known, and probably vary 

 in individual cases. Minot 3 suggests the following approximate times : 



Tumefaction of the mucosa, with accompanying structural changes 5 days. 



Menstruation proper 4 



Restoration of the resting mucosa ... 7 



Resting period 1- 



Total 28 da y s - 



The menstrua] changes in the uterus are accompanied by characteristic 

 phenomena in other parts of the body. The Fallopian tubes are congested, 

 l See Westphalen : Archivjur Qynakologie, 1896, lii. S. 35 ; and Mandl: Ibid., 8. 557. 

 2 T. A. Emmet- The Principle* and Practice of Gyrwecology, 1880, 2d ed. 

 S C. S. Minot: Human Embryology, L892. 



