of the mechanical, physical, and chemical properties of a body is contained in the vibration this body succeeds in propagating through our cerebral atmosphere. There is in this a phenomenon of transmission analogous to that which is produced when an air of music is sent along a wire; the whole concert heard at the other extremity of the wire has travelled in the form of delicate vibrations.
There must therefore exist, though unperceived by our senses, a sort of kinship between the qualities of the external objects and the vibrations of our nerves. This is sometimes forgotten. The theory of the specific energy of the nerves causes it to be overlooked. As we see that the quality of the sensation depends on the nerve that is excited, one is inclined to minimise the importance of the excitant. It is relegated to the position of a proximate cause with regard to the vibration of the nerve, as the striking of a key on the piano is the proximate cause of the vibration of a string, which always gives the same degree of sound whether struck by the forefinger or third finger, or by a pencil or any other body. It will be seen at once that this comparison is inexact. The specific property of our nerves does not prevent our knowing the form of the excitant, and our nerves are only comparable to piano strings if we grant to these the property of vibrating dif-
