An American text-book of physiology . the first to measure the rate of con-duction in nerves.* Originally he employed Pouillets method for measuringshort intervals of time. The arrangement is illustrated in Figure 32. Themoment that the current in the primary coil of an induction apparatus wasbroken and the nerve connected with the secondary coil received a shock,a current was thrown into the coils of a galvanometer (see p. 136). An instantafter, the contraction of the muscle wiiich resulted from the stimulation of thenerve broke the galvanometer circuit. The amount of deviation of the magneto
An American text-book of physiology . the first to measure the rate of con-duction in nerves.* Originally he employed Pouillets method for measuringshort intervals of time. The arrangement is illustrated in Figure 32. Themoment that the current in the primary coil of an induction apparatus wasbroken and the nerve connected with the secondary coil received a shock,a current was thrown into the coils of a galvanometer (see p. 136). An instantafter, the contraction of the muscle wiiich resulted from the stimulation of thenerve broke the galvanometer circuit. The amount of deviation of the magnetof the galvanometer varied with the time that the circuit remained closed, andtherefore could be taken as a measure of the interval elapsing between thestinmlation of the nerve and the contraction of the muscle. The nerve wasexcited in two succeeding experiments at two points, at a known distance apart,and the difference in the time records obtained was the time required for thetransmission of the nerve-impulse through this Fig. 32.—Method of estimating rate of conduction in motor nerve of frog, as used by horizontal bar a-b is supported on an axis in such a manner that when the contact is made at a it isbroken at b, therefore at the same instant a current is made in the galvanometer circuit and opened inthe primary circuit of the induction apparatus. When the muscle contracts, the galvanometer circuitis broken at c. The nerve was stimulated in two successive experiments at d and e. Later, Helmholtz devised a method of directly recording the contractionsof the muscle, and employed this to measure the rate of conduction in motornerves. He stimulated the nerve as near as possible to the muscle and re-corded the contraction, then he stimulated the nerve as far as possible from themuscle and again recorded the contraction. The difference in time betweenthe moment of excitation and the beginning of the contraction in the twoexperiments was due to the differ
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