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to ring a little bell. Here you see the shadow of the apparatus cast on the screen by the electric light. I intend to use electricity to stimulate or irritate the nerve or the muscle at pleasure, and I have so arranged the apparatus that I Fig. 9.—Arrangement of apparatus for irritating the muscle, g, directly, or the nerve connected with it at f. a, galvanic element; b, key; c, primary coil of induction machine; d, secondary coil; e, commutator by which current can be sent either to nerve or to muscle; f, electrodes, as in Fig. 8, for the nerve; g, muscle; h, small hammer; i, weight. can send a single shock to the nerve or muscle, or a number of shocks in quick succession. We have now got everything adjusted. Observe that when I send a shock to the nerve the muscle gives a twitch and pulls on the thread, and observe the little hammer striking; the bell. The muscle has contracted only