_Hydrosalpinx._--The fluid in a hydrosalpinx may be colorless, slightly yellow, or brownish or chocolate colored from the presence of blood. As the accumulation increases, the walls of the cyst atrophy and become very thin. The epithelium and the mucous membrane atrophy and in time disappear, until nothing but a thin-walled transparent cyst remains (Fig. 149). The cyst-wall in hydrosalpinx is always thinner and more transparent than that in pyosalpinx. On the inner wall of the cyst delicate ridges corresponding to the plicæ or folds of mucous membrane may be traced. There may often be discovered, at the distal end of the retort-shaped tumor, a slight depression that marks the position of the abdominal ostium, while upon the inner aspect of this depression may be found the remains of the invaginated fimbriæ. The size of the tube in hydrosalpinx varies from that of the little finger to a tumor as large as the fetal head. Large hydrosalpinx tumors are very unusual, because the fluid probably leaks slowly through the thin cyst-wall, and because the secreting surface of the cyst becomes destroyed by pressure. The fluid from a hydrosalpinx is sterile, unirritating to the peritoneum, and is readily absorbed. The cyst may rupture spontaneously or as the result of some slight accident; the fluid will be absorbed by the peritoneum, and only the shrivelled, atrophied sac will remain. In old cases of this kind the Fallopian tube is represented by an impervious cord. Such specimens have often been found in old prostitutes who have survived the dangers of their calling. _Hematosalpinx._--True hematosalpinx, a closed Fallopian tube distended with blood, is a rare condition. Tubal pregnancy is the usual cause of an accumulation of blood in the Fallopian tube, but the term hematosalpinx should not be applied to this condition. True hematosalpinx occurs when, from any cause, hemorrhage takes place into a tube that had previously been closed by inflammatory action. Such an accident may be caused by traumatism or by torsion of the pedicle of a tubal cyst. Slight hemorrhages of this kind occur in pyosalpinx and in hydrosalpinx, and cause the brownish discoloration that is sometimes seen in the contents of these tumors.