Both in these experiments, and in all my others, where a comparison was instituted between the two legs of the same frog, I divided equal portions of skin on both thighs, that there might be no unequal exposure of the muscles to the water, which would have occasioned a fallacy in the result. EXPERIMENT II. On the 31st of March last, I divided, in two, a frog, in one of whose legs I had four months before excited inflammation, by laying bare the crural artery and nerve. The inflammation had been so violent and general, that the frog lost its cuticle in consequence of it, and, when compared with a healthy frog, its resperation was observed to be remarkably frequent. Three weeks after this, when the wound in its thigh had perfectly skinned over, I laid it open again, and divided the sciatic nerve. No general inflammation this time took place, nor did the wound again skin over; but for about a month before it was killed, a large ulcer had formed immediately over the division of the nerve, but had not proceeded down to it. The limb, at the time I killed the frog, was as destitute both of motion and of sensation, as at the first instant the nerve was divided, but contractions were excited in it, by touching the ulcer with zinc and silver. When the frog was dead, however, the contractions were found much more feeble in this than in the other leg. The metals were now applied to the sciatic nerves within the abdomen. Vigorous contractions were excited in the sound leg, but none in that whose nerve had been divided. Hence it was plain, that no actual regeneration had taken place. On examining the nerve accurately at the part divided, I found the divided ends, which had receded considerably from each other, connected by a transparent gelatinous substance. From the upper end, which appeared elongated into a conical form, several red streaks projected into the interposed substance. The lower end was opaque, thickened, and rounded. No appearance of spiral bands could be detected, either in the interposed substance, or in the part of the nerve below the division, when these parts were examined with the assistance of a microscope. This substance had attained sufficient consistence to support the under part of the nerve, when the upper was raised with a pair of forceps. The leg, in which the nerve had been divided, continued to contract as long as the other, though much less vigorously, and the part, from which I could longest excite contractions, was the ulcer. EXPERIMENT III. On the 14th of April last, I killed two other frogs, by dividing their hind extremities from their bodies. In one, the right sciatic nerve had been divided more than six weeks previous to its death. In the other, one of the sciatic nerves had been divided between three weeks and a month.