A good physiological experiment like a good physical one requires that it should present anywhere, at any time, under identical conditions, the same certain and unequivocal phenomena that can always be confirmed.

It is exceedingly improbable that the identical action of the corresponding parts of the two retina is the result of a certain habituation, or of the influence of the mind.

We shall probably never attain the power of measuring the velocity of nervous action; for we have not the opportunity of comparing its propagation through immense space, as we have in the case of light.

The organizing principle, which according to an eternal law creates the different essential organs of the body, and animates them, is not itself seated in one particular organ.

Sensation is not the conduction of a quality or state of external bodies to consciousness, but the conduction of a quality or state of our nerves to consciousness, excited by an external cause.

The cooperation of the two retina in one field of vision, whatever is its cause, must rather be the source of all the ideas to which single or double vision may give rise.

To speak, therefore, of an electric current in the nerves, is to use quite as symbolic an expression as if we compared the action of the nervous principle with light or magnetism.