The discovery was confirmed by several physiologists between 1830 and 1850; and I do not think we have the right to repeat this cruel experiment for the sake of the instruction of students. It is not only cruel, but also useless, for it consists in laying bare the anterior and posterior nerve-fibres of the spinal cord, with the sole object of allowing students to see that the excitation of the anterior nerve-fibres provokes movement and not pain, whilst the excitation of posterior nerve-fibres provokes pain and not movement. Now, in order to make students clearly understand this distinction between the motor and sensory nerves, I require only a blackboard and a piece of chalk; and I claim that, with a piece of chalk and a blackboard, I am able to explain very clearly all the details of this phenomenon. Not only does the chalk suffice for comprehension as well as vivisection, but it is better; because the experiment is so delicate, so difficult, and, in order to be understood, it must be observed so narrowly, so closely, that out of the whole class scarcely two or three students are able to follow the experiment. The rest of the class have before them only the frightful spectacle of the reactions of a mutilated, suffering animal under excitations which are made in the very depths of a wound on organs which they do not see. This experiment is rendered more particularly cruel by the fact that anæsthetics cannot be used, precisely because the point in question is the sensibility or non-sensibility of the animal, and consequently by its very nature the operation cannot be made on the insensible animal.[1] And now, at once entering further into the difficulty of the problem of vivisection, we may ask ourselves if we have the right to allow demonstrations of experimental physiology on living animals that have been rendered insensible by chloroform. Although, further on, I intend coming back to this important question of anæsthetics, I will say at once I do not understand what repugnance there can be to operating upon an anæsthetised animal. Once he is insensible he cannot suffer; why hesitate, therefore, to perform prolonged experiments upon that insensible being? It appears to me just as inhuman to boil milk as to excite the pneumogastric nerve of a dog rendered incapable of suffering. The milk does not suffer; the dog does not suffer; in both cases it is living matter, but insensible living matter. Consequently, as far as physiological demonstrations are concerned, every individual capable of reflection should recognise that there is nothing wrong in experimenting upon animals that cannot suffer.