In these experiments various surgical procedures were employed, with the hope of finding a method for stimulation of the longitudinal growth of bone. The first three groups of experiments (a repetition with minor modifications of the procedures of Meisenbach, Pearse, Ferguson, and others) failed to produce significant increase in the length growth.

By chance, in several animals, we observed that stimulation of the length growth was produced by the simple procedure of loosening or stripping the periosteum from the shaft of the bone. Consequently, this operation was repeated on twenty-two animals, with quite uniform and significant results, as shown in Table IV. With but three exceptions out of twenty-two rabbits, the operated leg showed definite lengthening when compared with the normal leg on the opposite side. Although the amount appeared to be small, it actually represented an increase of from 5 to 15 per cent. over the normal growth of the bone during that period of time. Observations of the monthly roentgenograms showed that the most active stimulation of length growth of the bones took place during the first three months following the operation.

We are unable to give a definite explanation of the factors which, after the periosteum had been stripped, produced this stimulation of the longitudinal growth.