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, and the integrity of this nervous influx that the consciousness is closely linked. It there finds one of the conditions of its apparition.

2. On the other hand, the consciousness remains in complete ignorance of these intra-cerebral phenomena. It does not perceive the nerve-wave which sets it in motion, it knows nothing of its peculiarities, of its trajectory, or the length of its course. In this sense it may be said that it is in no degree an anatomist; it has no idea of all the peculiarities of the nerve-wave which form part of its cerebral history from the moment when these peculiarities are out of relation with the properties of external objects.

One sometimes wonders that our consciousness is not aware that the objects we perceive with our two eyes correspond to a double undulation, namely, that of the right and that of the left, and that the image is reversed on the retina, so that it is the rods of the right which are impressed by objects on our left, and the rods of the upper part by objects below our eyes. These are, it has been very justly said, factitious problems, imaginary difficulties which do not exist. There is no need to explain, for instance, direct vision by a reversed image, because our consciousness is not aware that the image on the retina is reversed. In order to take account of this, we should require another eye to see this image.