According to _Gebhard_, three stages may be distinguished. The first stage is that of premenstrual congestion, or stage of engorgement: the capillary vessels of the mucous membrane become distended with blood, the membrane itself becomes softened, the meshes of the stroma become enlarged and are filled with the morphological constituents of the blood, subepithelial hæmatomata are formed. The second stage is that in which the blood finds its way to the exterior: owing to the turgescence of the mucous membrane the blood is able to exude between the cells of the intact epithelium; further, the epithelium becomes lacerated in various places where hæmatomata have formed beneath it, allowing the blood to exude through the apertures thus formed; shreds of epithelium may be washed away by the blood-stream. The third stage is that of post-menstrual regeneration: the swelling of the mucous membrane disappears, the detached areas of epithelium readhere, the blood effused into the interstices of the tissue is reabsorbed, or is in part transformed into yellowish-brown flakes of pigment. According to _Gebhard’s_ view, during menstruation destruction of the uterine mucous membrane does not occur. At no time is the membrane denuded of large areas of epithelium; a very active process of regeneration occurs, however, in the superficial epithelium and the epithelium of the glands, which fits the uterine mucosa for the reception of the fertilized ovum by keeping it in an ever-young and renovated condition. The mucous membrane of the cervix takes part in menstruation at most by an increased secretion of mucus. According to _Landau_ and _Rheinstein_, the mucous membrane of the Fallopian tubes contributes to the menstrual hæmorrhage; _Fritsch_ and _Strassmann_, however, are opposed to the view that there is a regular tubal menstruation. _Pathology of Menstruation._ Only a small proportion of girls and women are entirely free, at the time of menstruation, from all change both in their bodily and in their mental state. A very great majority complain of feeling more or less unwell, of sensations of weight and pressure in the hypogastric region, of a general feeling of languor, loss of appetite, headache, irritability, sometimes of an inclination to weep; in women, a change in the intensity of the sexual impulse manifests itself, an increase in some, a decrease in others. Not infrequently during menstruation, the cardiac activity is notably affected, so that, regularly at the commencement of each period, disagreeable sensations occur in the cardiac region, with increased frequency of the heart’s action; or complaint is made of coldness and dampness of the hands, of icy coldness of the feet, which feel as if “dead” to half way up the calves, and cannot be warmed—phenomena which, in the cases under consideration, occur only at the time of menstruation, and are to be regarded as manifestations of the menstrual reflex.