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168 of light slowly sails back to the original point. You will recollect that when the right-hand trough was positive, the spot travelled to the right, as we have just seen.

Pursuing the experiment farther, I now pick up the muscle with the forceps and place it again on the pads, but in a reversed position; that is to say, the surface now touches the pad on the left, while the section is in contact with the pad on the right. I again close the key, and you now see the spot passes to the left and takes up a position on that side. Open the key, and it again sails back. Remember, once more, that the spot should come to the left when the left pad is positive, as has occurred in this last experiment. These two experiments clearly prove, first, that a muscle at rest gives a current; and, second, that this current travels through the galvanometer circuit from the surface of the muscle to the transverse section. The surface of the muscle is thus positive to the transverse section; or you may get a clearer notion of the statement by supposing the bit of muscle to be a little galvanic element or battery. In that case, the surface of the muscle is the positive pole,