1. When two dissimilar metals were joined together and inserted into the metaphyses of the long bones of puppies, ten to fourteen weeks old, as close to the epiphyseal line as possible, stimulation of longitudinal growth was sometimes obtained. This growth was apparently not sustained, however, for it was found only in animals which were sacrificed from one to four months after the operation. The amount of growth obtained varied from one to five millimeters.
2. The animals in which an increase was obtained constituted 36 per cent of all the experimental animals, and if the animals in which epiphyseal damage occurred at the time of insertion are excluded, the percentage rises to 52. Of the dogs in which the larger plate-type electrodes were inserted without resulting epiphyseal damage, 71 per cent showed an increase in length. The most consistent results were obtained with the use of copper and constantan.
3. In some animals the unit was inserted into the growth center itself or into the epiphyseal line. This procedure resulted in shortening of the bone.
4. In one control series of animals the same operation was performed without insertion of the metals. This group showed no uniform increase in growth, although in one animal there was a growth increment of three millimeters. In another series of control animals the ununited metals were inserted into the metaphysis; this group also showed no growth stimulation. It has not been shown that operative trauma or metallic corrosion were directly responsible for any increase in length.
5. The performance of a fibular osteotomy had no effect upon growth under the conditions of this experiment. Comparable growth increments were obtained in the animals with and without osteotomy.
6. A series of children were also subjected to this method of epiphyseal stimulation with no appreciable increase of growth noted. Perhaps this negative result was due to the small mass of the metals employed. No ill effects were noted from these procedures in any patient, but further experimental work must be done before this method is again employed in children.
7. It is felt that the increased growth which was obtained in this study was due to electrolytic stimulation, the intensity of this stimulation varying directly with the surface area of the electrodes employed. No ill effects resulted from the presence of the metals in the dogs, even after four years.