Eight animals died from 1 to 6 years after the operation, from undetermined diseases, or from pneumonia. Two animals are still alive 7 years after the operation.

1. Condition of the Pleural and Pericardial Cavities.—In the first experiments, extensive pleural and pericardial adhesions were observed 1 year and more after the patching of the pulmonary artery. There was also a great deal of fibrous tissue between the pulmonary artery, the aorta, and the left auricle. In the other experiments, the adhesions of the lungs, pleura, and pericardium were less marked. This was due to some improvements in the technique of handling the viscera. At the time of the operations, it was hoped that no pleural or pericardial adhesions would occur. Great care was taken not to injure the endothelial surfaces by rough handling or by sponging. No blood was allowed to flow into the pleural cavity. The surface of the pericardium was protected by fine silk membranes. The pleural cavity was occluded by thick pads made of cotton and Japanese silk. It seemed that the serous surfaces were almost completely protected against infection and mechanical irritation. The occurrence of primary pleurisy and pericarditis was prevented by this technique. But the development of adhesions in several of the experiments shows that the procedures for the handling of the viscera should be perfected.

2. Condition of the Arterial Wall.—In the experiments in which the orifice was patched, a slight dilatation of the artery was observed. It was not possible to ascertain from the specimen preserved in formaldehyde whether or not there was an insufficiency of the valves. It is probable that there was no leakage, as in none of these cases could any diastolic murmur be heard 6 months after the operation. The only animal which presented clinical evidence of pulmonary insufficiency died during the War. The normal condition of the pulmonary orifice was due to the incision which did not extend far enough on the ventricle, and to the power of redintegration possessed by an organ which is not diseased. The cicatrization of the grafted flap was excellent. Its outline could not be seen on the external side of the wall. Even after opening the artery, the transplant could not be located easily. However, in Experiment 1 the anterior wall of the artery showed a depression about 7 or 8 mm. wide, 18 mm. long, and 2 or 3 mm. deep, behind and above the anterior valve. But the flap was made of human artery, and it is known that a heteroplastic graft always undergoes some dilatation. When transplants of dog tissue were used, no dilatation occurred and the location of the patch could hardly be detected. In Experiment 7, 6 years after the operation, the endothelial surface was smooth, glistening, and no scar could be seen. However, the upper and lower parts of the incision were marked by a slight depression of the wall. The presence of the patch was detected by a distinct thickening of the wall. Although the edges of the incision had not been sutured to the edges of the flap, the endothelial surface was quite smooth. A transverse section of the artery was made through the middle part of the flap in Experiment 4. It showed the width of the arterial opening and the way in which the transplant became adherent to the arterial wall. The examination of these four specimens demonstrated that, in spite of the unfavorable location of the graft, an excellent union had taken place. It showed that homoplastic or heteroplastic tissue can be transplanted onto the pulmonary artery as well as onto the smaller arteries. Where the arterial wall had simply been incised without interposition of a patch, a linear scar was always found. 6 years after the operation, the incision used in the course of an operation for cauterization of the sigmoid and sutured with heavy thread was transformed into a linear scar and the surface of the intima was quite smooth.

3. Condition of the Sigmoid Valves.—In three experiments, the sigmoid valves had been cauterized along their margin and their point of insertion in the artery. One of the animals was still living 7 years after the operation. There was no diastolic murmur. The other animals died 3 and 6 years after the operation. The valves were thin and transparent, and quite normal. However, one of the valves showed two holes, one near the base and the other near the margin.

The animal on which the section of the right posterior valve without suture was performed, died 2 or 3 years after the operation. The edges of the incision had not united. They were thickened and the whole valve was rigid. The surface was rough and irregular.

No permanent result was obtained by the union of two sigmoid valves by a stitch. There was no stenosis of the orifice, and no union of the valves 4 years after the operation. The stitch had disappeared. There was some scar tissue at the common point of insertion of the posterior valves, which were more rigid and showed thickened edges. 7 years after the section and suture of a sigmoid had been performed, the animal was still living and in good health. No diastolic murmur could be detected.

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