mal muscle. It was in no way connected with the former line of incision. There was no fat present in the muscle cells of any of the sections. In as much as fever was present as a complication in only four of the cases, one would conclude that foreign material, either blood or lochia, prevented a firm union of the scar in the other five. The very fact that decidua covered the edges is sufficient to prove that these margins were separated when the patient became pregnant.

Five moderately strong scars were found on examination of the

Fig. 7-Section from Case No. 19 and shows excessive fibrous tissue in the subperitoneal structures. It is limited however, for a normal amount of muscle is also observed in this field.

whole scar or margin only. In two of these there was no fever after the previous section; in two the previous history was not obtained, and in one the patient had some temperature. Miscroscopical examination of one of these scars showed a small area in which the muscle was replaced by a delicate fibrous tissue network, and in another there was more extensive proliferation of fibrous tissue beneath the peritoneum (Fig. 7) than is usually observed. In four the placenta was attached directly beneath the wound, which shows that the location of the placenta had little effect

on the scar providing there was firm union after the previous operation. There were six cases in this series which presented thin scars varying from peritoneum only between the edges of the myometrium, to different amounts of muscle tissue. Three of these had fever following the preceding operation, and an excess of fibrous tissue was not observed in any of them.

Examinations were made of the line of incision of the former operation in six different cases, two of which were thick and four were thinned

Fig. 8-Section from case No. 14, shows the margin of the poorly united incision with fibrous tissue adjacent to the decidua. It has replaced some of the myometrium.

out. The interval between the last section and the operation was from one to three years. One of the four was a moderately thick scar throughout, but it presented one small area in which the myometrium had been replaced by short connective-tissue fibers. Another varied in thickness from 2 mm. to 1.2 cm. and the thicker area consisted of myometrium which was identical in every detail with the myometrium in adjacent areas. All presented thickened peritoneum with some subperitoneal proliferation of fibrous tissue.

CONCLUSIONS.

1. The strength of the uterine scar after Cesarean section depends upon the absence from the wound of infection and foreign material and upon the perfect coaptation of the incised surfaces.

2. A perfectly healed wound leaves the myometrium as strong after operation as before, as far as can be determined by the histological examination of the tissue in the line of the former incision.

Fig. 9

Section from case No. 13, from the margin of the rupture of the former scar. The upper angle snows that the scar was almost entirely composed of peritoneum, beneath which are numerous placenta villi. Decidua are also observed along the former incised surface.

3. A continuous suture in the myometrium adjacent to the decidua may assist in preventing the separation of the cut surfaces by blood clot or lochia in addition to the usual interrupted suture through serosa and myometrium.

4. The placenta in a subsequent pregnancy has little or no effect in weakening the firmly united scar, but if the scar is already weak it may accentuate this weakness.

5. Other than a small amount of fibrous tissue beneath the peri