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 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:

1st. Rupture of blood-vessels in the pelvis:
Utero-ovarian;
Varicose veins of broad ligaments;
Vessels of extra-uterine ovisac.
2d. Rupture of pelvic viscera:
Ovaries;
Fallopian tubes;
Uterus.
3d. Reflux of blood from the uterus:
Menstrual blood.
4th. Transudation from blood-vessels:
Purpura;
Scorbutus;
Chlorosis;
Hemorrhagic peritonitis.

It is then clear that the mere presence of a large clot of blood in the pelvis, apart from general symptoms, is a matter of very doubtful significance, since on the one hand it may be the result of a mere regurgitation of menstrual blood due to imperviousness of the cervical or tubal canal, or on the other of the rupture of a Fallopian tube which has become the nidus of an extra-uterine foetus.

Whatever be the source of the blood which escapes, it coagulates, unless very poor in fibrin, either in the most dependent part of the peritoneum or in the pelvic areolar tissue beneath it. Here the watery portions of the mass are gradually absorbed, leaving a hard, small tumor remaining; or, suppurative action being excited, the hard mass is softened down and discharged into the rectum, vagina, bladder, or peritoneum as a grumous material somewhat resembling currant-jelly in appearance.

CAUSES.—These must be divided into predisposing and exciting, for it is rare to meet with the disease in a woman who has previously been in perfect health. The predisposing causes which can be cited with confidence are—the period of ovarian activity (fifteen to forty-five years); disordered blood-state, plethora or anæmia; the menstrual epoch; chronic ovarian or tubal disease; pelvic peritonitis; and the hemorrhagic diathesis. The exciting causes have been found to be sudden checking of the menstrual flow; blows or falls; excessive or intemperate coition; obstruction of cervical canal; obstruction of Fallopian tubes; violent efforts; and ectopic gestation.

VARIETIES.—The two great classes of the affection are the peritoneal and the subperitoneal. In the former the blood collects in the peritoneal cavity and becomes encysted there; in the latter it collects in the cellular tissue beneath the peritoneum, and there forms a solid mass.