The pain in this form of dysmenorrhoea generally does not precede the flow. In character it is sometimes like colic, but its leading feature is expulsive effort. It occasionally so nearly resembles abortion as to require care to distinguish between them. It is frequently intermittent, presenting intervals of complete relief. In severity it varies widely. In some cases the patient assumes and maintains a certain position which she has learned affords her some relief. This indicates with great probability uterine distortion from fibroid tumor. The writer has met with a marked instance of this kind. The flow is more irregular in this than in other forms. It is sometimes extruded drop by drop; more often it appears in gushes, the fluid accumulating and distending the uterus until expulsive efforts are excited. Clots are often thrown off under these circumstances in shape and size corresponding to the cavity of the uterus. Absence of prodromata, presence of the fluid being necessary to excite the pain, the intermittent and especially the expulsive character of the pain, and the kind of clots, indicate the nature of the case. A certain diagnosis, however, rests alone on physical examination. This should be by the touch, bimanual and rectal, and the sound. Sometimes additional aid will be derived from the speculum. By touch the form, size, shape, and direction of the cervix are ascertained, and its relations to the body of the uterus. The sound will give evidence as to the patency and direction of the cervical canal and uterine cavity. A diagnosis of obstructive dysmenorrhoea should not be rejected because the patient occasionally passes a period without pain. In the male an enlarged prostate may for a long time interfere but little with micturition, and then all at once completely obstruct the flow of urine. A diagnosis cannot be based alone upon the condition of the cervical canal as found during the intermenstrual period. Two elements are to be considered, each of which may, and doubtless often does, play a part: tumefaction from the congestion attendant on the process, and spasm. The latter, caused by reflex action excited by irritation in the body of the uterus, assumes a leading position with those who claim that obstruction is the {195} sole cause of dysmenorrhoea. That it plays an active part in many cases cannot be doubted; that it is a necessary condition of even spasmodic dysmenorrhoea is disproved by the positive statement of Matthews Duncan, that in some cases he could pass a sound freely into the uterus during the paroxysms.