The discharge in dysmenorrhoea varies very widely in amount and character. It may be so scanty as to border on amenorrhoea or so profuse as to be menorrhagic. It may be more or less fluid than usual. The expulsion of clots is a frequent feature, and the size and shape of these sometimes give indications of value. Like other uterine derangements, dysmenorrhoea is not a disease per se, but a symptom of some pathological condition the exact nature of which is to be ascertained whenever possible. Cases may be classified as follows: I., Obstructive or mechanical; II., congestive; III., neuralgic; IV., membranous. It cannot be too distinctly kept in view that this classification, like many others, cannot be rigidly followed. The dividing-lines are sometimes but faintly drawn by nature; some cases present the features of more than one class; some by natural progress pass from one class into another. Based upon leading clinical features, this classification will assist in the study of the subject, facilitate diagnosis, and aid in directing therapeutic measures. Two classes given by some authorities are not included in the above classification. They are spasmodic and ovarian dysmenorrhoea. If by the former is implied painful contractions of the uterus during menstruation, the cases fall into the first class given above, the obstructive; and if irregular nervous action is implied, they belong to the third, the neuralgic. The term ovarian has been applied to those cases in which an abnormal condition of the ovaries exists, such as inflammation, enlargement, or dislocation. Such conditions are not easily ascertained during life; if ascertained, the fact throws light on the etiology of the case; but for {194} treatment the case will range itself, according to the clinical features it presents, among those in which the vascular or the neurotic element predominates. Obstructive or mechanical dysmenorrhoea is that form in which some impediment exists to the free escape of the menstrual discharge. The genital canal presents no exception to the general rule that when an excretory channel is obstructed violent and painful expulsive efforts are excited. The causes which give rise to the obstruction are various. Among them are the following: fibroid tumors of the uterus distorting, and polypi obstructing, its cavity or neck; stenosis of the cervical canal, either congenital or acquired, the latter often the result of the injudicious use of strong caustics; a long and conical cervix; a contracted os, sometimes so small as to be justly termed the pinhole os; versions and flexions of the uterus. The seat of obstruction is almost always uterine, but may be in the vagina or at its entrance. There is much difference of opinion as to the relative frequency of occurrence of obstruction at the internal or external orifice of the cervix.