The capsule of the ovary becomes thickened, and rupture of the ripe ovarian follicles is prevented. Small cysts throughout the ovary are formed in this way. Two or more cysts may become converted into one cavity by absorption of the intervening walls, so that cystic spaces of larger size, equal to that of a duck-egg, may result. Such cysts may become infected by pyogenic organisms from the tube, and an ovarian abscess is produced. [Illustration: FIG. 148.--Tubo-ovarian abscess.] _Tubo-ovarian Abscess._--If the tube is brought into immediate contact with the ovary, either by agglutination of the fimbriated end to the surface of the ovary, or by adhesion of the side of the tube to the ovary, or by burrowing between the layers of the broad ligament, the tissue intervening between the cavity of the tube and the cyst of the ovary may be absorbed or perforated, and the two cavities will be thrown into one, forming a tubo-ovarian abscess or a tubo-ovarian cyst (Fig. 148). The opening between the tubal and ovarian portions of the cyst does not usually correspond to the abdominal ostium of the tube, but may be an adventitious opening in the side of the tube (Fig. 148). _Pyosalpinx._--When the Fallopian tube is distended with pus or with other fluid, its walls gradually become thinned. In this respect the Fallopian tube differs from the body of the uterus, in which a hypertrophy of the muscular coat usually takes place, under the influence of distention from the presence of retained fluid within it. This gradual thinning of the tube-wall predisposes to rupture or leakage and the escape of the contents into the abdominal cavity. A pyosalpinx often becomes adherent to the rectum, the small intestine, or the bladder. The wall of the intestine or the bladder becomes perforated, and the pus is discharged in this way. It seems probable that in some unusual cases the obstruction in the lumen of the tube is temporarily overcome, and that evacuation takes place through the uterus, followed by refilling of the tube. This, however, is a very unusual occurrence, and is not frequent, as is assumed by some writers. The evidence of such discharge is based only on clinical observation. There is no good pathological evidence of such an occurrence. It is probable that in most of the reported cases the purulent or watery discharge which escaped in a sudden gush was derived from, and had been retained in, the body of the uterus. The pus of pyosalpinx varies greatly in character. In the early stages of the disease it is actively septic and contains a variety of micro-organisms. These organisms are the gonococcus, streptococcus, staphylococcus, the bacillus coli communis, the tubercle bacillus, and the pneumococcus.