FREQUENCY.--It may be said, in general terms, that this affection is by no means rare, every one of large experience in gynecology meeting necessarily with a large number of cases of it. But no reliable statistics of its frequency have been collected up to the present time. Olshausen of Halle declares that in 1145 gynecological cases he saw 34 hæmatoceles; Beigel in 2000 cases found 38; Schroeder, 7 in 1000; and Seiffert of Prague reports 66 seen in 1272 cases of female pelvic diseases. Barnes says that in ten years' practice he met with 53 cases, and in twenty years Tilt has seen but 12. Without doubt, the validity of the statistics of this disorder is vitiated by erroneous diagnosis, as is the case with all affections which generally end in recovery. Here cases of cellulitis, pelvic peritonitis, imprisoned cysts, etc. offer prolific sources of error, as I can aver from the results of my own experience. PATHOLOGY.--It is a fact, thoroughly proved by physiological experiment, that blood injected into serous cavities very soon encysts itself by the enveloping influence of lymph which is poured over it, forming false membranes, or, as the French term them, néo-membranes. The clot, once formed, clings to the serous membrane in contact with it, and soon becomes roofed over by lymph, which, according to Vulpian, begins to show traces of organization as early as the end of twenty-four hours. Should the effused blood be poor in fibrin, the coagulation and encysting do not occur, a rapid absorption taking the place of these processes. Pelvic hæmatocele consists, as has been already stated, in the collection of a mass of blood in the pelvis, either above or below its roof, without reference to the source of the flow. Such a flow ordinarily occurs from one of the three following sources: first, rupture of vessels in the pelvis; second, reflux of blood from the uterus or tubes; third, transudation of blood in consequence of dyscrasia or pelvic peritonitis. From this it becomes evident that hæmatocele is not a disease, but a symptom which marks a number of different pathological conditions of quite various significance. As, however, we cannot discover the original accident or pathological condition, we are forced to compromise with {241} taking its most prominent sign as the exponent of a state which is beyond the powers of diagnosis. Autopsic evidence has revealed the following as the special and most frequent sources of the hemorrhage: