A short time since, the following scene took place in a street adjoining Hanover-square. It was an exhibition of a highly interesting character, and worthy to be placed upon record. The editor of the Lancet having heard that a French gentleman (M. Léonard), who had for some time been engaged in instructing two dogs in various performances that required the exercise, not merely of the natural instincts of the animal and the power of imitation, but of a higher intellect, and a degree of reflection and judgment far greater than is commonly developed in the dog; was residing in London, obtained an introduction, and was obligingly favoured by M. Leonard with permission to hold a 'conversazione' with his extraordinary pupils. He thus describes the interview: Two fine dogs, of the Spanish breed, were introduced by M. Leonard, with the customary French politesse, the largest by the name of M. Philax, the other as M. Brac (or spot); the former had been in training three, the latter two, years. They were in vigorous health, and, having bowed very gracefully, seated themselves on the hearth-rug side by side. M. Léonard then gave a lively description of the means he had employed to develop the cerebral system in these animals--how, from having been fond of the chase, and ambitious of possessing the best-trained dogs, he had employed the usual course of training--how the conviction had been impressed on his mind, that by gentle usage, and steady perseverance in inducing the animal to repeat again and again what was required, not only would the dog be capable of performing that specific act, but that part of the brain which was brought into activity by the mental effort would become more largely developed, and hence a permanent increase of mental power be obtained. This reasoning is in accordance with the known laws of the physiology of the nervous system, and is fraught with the most important results. We may refer the reader interested in the subject to the masterly little work of Dr. Verity, "Changes produced in the Nervous System by Civilization." After this introduction, M. Léonard spoke to his dogs in French, in his usual tone, and ordered one of them to walk, the other to lie down, to run, to gallop, halt, crouch, &c., which they performed as promptly and correctly as the most docile children. Then he directed them to go through the usual exercises of the 'manége', which they performed as well as the best-trained ponies at Astley's.