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Rh the break is opened will practically coincide with the moment the nerve receives the shock, because the electricity travels with such enormous rapidity in the coils and along the wires to the nerve as to make the time between opening the break and irritating the nerve practically nothing. If I knew the moment the nerve was stimulated, it would be interesting to ascertain if the muscle contracted at that moment. Now we can easily record this moment by first of all causing the muscle to contract by bringing the car slowly up to the break till it opens it. When the muscle contracts, it makes a mark, which indicates the moment the break will be opened when we perform the actual experiment. At that moment the nerve is irritated, and if the muscle contracts at the same instant, the beginning of its upward curve should exactly coincide with the mark of the signal. Now we shall perform the experiment. Mr. Brodie has got the railway ready for starting. He opens the break, releases the catch, and lets the glass plate dash onwards. The muscle, of course, does not contract, as the nerve has not received a shock, and