Note 109 — Chapter III · NEURILITY.

In 1859 I mentioned that if the nerves of a frog’s back be exposed by raising the skin, they may be pricked or even cut without sensible effect, although a slight prick on the skin will excite the nerves, and cause a reflex action. In 1870, Prof. Fick expressed his astonishment at finding that after he had cut out a piece of the skin, leaving it attached to the body by a single nerve, electrical stimulation of this excised skin caused the frog to make the reflex movement of rubbing the irritated surface; whereas electrical stimulation of the nerve-trunk itself produced no reflex effect, only a twitching of a muscle. Pflüger’s Archiv, 1870, p. 327. Brown Séquard tries to establish a distinct species of nerves as conductors of sensitive impressions, from those which are impressionable. The facts on which he founds these two properties simply show that nerves are so disposed that the stimulus which excites them in one place fails in another. He could hardly maintain that a skin nerve contained impressionable fibres at its periphery, and only conducting fibres in its trunk! See his communication to the Royal Society, Proceedings, 1856; and Lectures in the Lancet, 10th July, 1858.