distinction between spirit and matter, and of a reconciliation between them. But we will leave this first point and come to the second.
The second fact brought forward consists in what was long termed the 'specific energy of theObjection drawn from the so-called 'specific energy, of the nerves.—Reply. nerves.' We know that stimulation of the optic nerve by an external shock or by an electric current will produce a visual sensation, and that this same electric current applied to the acoustic or to the glosso-pharyngeal nerve will cause a sound to be heard or a taste to be perceived. From these very particular facts have been deduced two very general laws: that different causes acting on the same nerve excite the same sensation; and that the same cause, acting on different nerves, provokes different sensations. And from these laws it has been inferred that our sensations are merely signals, and that the office of each sense is to translate into its own language homogeneous and mechanical movements occurring in space. Hence, as a conclusion, the idea of cutting our perception into two distinct parts, thenceforward incapable of uniting: on the one hand homogeneous movements in space, and on the other unextended sensations in consciousness. Now, it is not our part to enter into an examination of the physiological problems raised by the interpretation of the two laws: in whatever way these laws are understood, whether the specific energy is attributed to the nerves or whether it is referred to the centres, insur-
