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FIGS. 4, 5, 6. At 3 the subject was directed to contract generally the muscles of the limbs, trunk and head; at o he was relaxed, while at I there was an intermediate degree of general contraction. The most marked start is here shown where the preceding neuro-muscular tonus is highest, while with relaxation there is no start.

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several visits to the Willard State Hospital of New York. They seemed too few in number, however, to permit more than a provisional generalization, particularly since marked exceptions to the rule often proved puzzling. In 1921-22, therefore, thanks to Professor Carr, the experiments were continued by Miss E. Lodor and myself at the University of Chicago, and later by Miss M. Miller who used a pistol to set off the start. The attempt was again made to record movements of the trunk, but in spite of attempted refinements, the graphs seemed crude and inadequate. Sommer's tri-dimensional analyser did not seem well adapted to our purposes; for we did not know in advance what parts would jerk or what directions they would take.

At this stage it seemed necessary, in order to get the large number of precise observations required for scientific generalizations, to restrict the study to the movements of some particular part of the organism. Thereupon the classical studies of the flexion reflex in physiology came to mind. It was evident that a quantitative inquiry into this reflex could be made in terms of speed and extent of movement, so that the influence of relaxation might be studied under more accurate conditions. If, in response to a sudden strong stimulus, the flexion reflex should be found to be diminished in the presence of general relaxation, this would agree with the results of the present article and tend to support its conclusions. These experiments on the flexion reflex are described below in the article by Miss Miller. The above discussion and results, although still to be regarded as provisional, meanwhile provide a larger setting for this work.

Summary. The observations presented suggest that both the sensory and the motor responses of the organism to a sudden strong stimulus depend upon the preceding general state of muscular tonus; that the feeling of 'shock' is weak or absent and the start is wanting or minimal where the individual is extremely relaxed.

We do not here mean 'relaxation' in the popular sense. An individual may be 'relaxed,' in this sense, yet start vio

lently at a sudden noise. Such partial relaxation may produce an apparent increase in the reflex because of a diminished contraction of muscles antagonistic to the movement of the start. This fact is also familiar in clinical tests of the kneejerk, where the subject is requested to 'relax,' in the popular sense, in order to permit the jerk to appear. But in real and extreme relaxation the knee-jerk has been shown to be reduced or entirely absent (3), a result which harmonizes with the article which immediately follows.

REFERENCES

1. LEHMANN, A. Die körperlichen Aeusserungen psychischer Zustände, Leipsig, Bd. i, 1899.

2. FÉRÉ, C. Sensation et mouvement, Paris, 1900.

3. JACOBSON, E., and Carlson, A. J. Amer. J. Physiol., 1925, 73, 324.

CHANGES IN THE RESPONSE TO ELECTRIC SHOCK PRODUCED BY VARYING

MUSCULAR CONDITIONS 1

BY MARGARET MILLER

The general problem of this experiment was to determine the effect of various conditions of muscular contraction and relaxation on the non-voluntary response to an electric shock. The stimulus was an induced current applied for a fraction of a second to the fingers, and the response measured was the upward jerk of the arm which followed. The shock was given without warning, and the subject was instructed not to attempt any voluntary control of his reaction. Graphic records of the reaction showed the extent of movement and the reaction-time.

The present paper deals with the first part of the experiment, in which the response made during extreme relaxation was compared with that obtained during ordinary rest upon a couch. The persons who served as subjects received preliminary training in inducing relaxation from Dr. Edmund Jacobson. At the end of this training they were able to assume and to maintain a state of general muscular relaxation which differed radically, in the judgment of subjects and experimenter, from the ordinary muscular condition.

APPARATUS

The subject lay on a couch with the tips of two fingers of the right hand immersed in two cups of normal salt solution. The stimulating current was passed through this solution, producing ordinarily a quick withdrawal of the hand. For each individual a particular strength and duration of current were selected and kept the same throughout the experiment,

1 The experiment was conducted in the Psychological Laboratory of the University of Chicago. The problem was suggested by Dr. Edmund Jacobson and the procedure carried through with his assistance and advice. The author is indebted to Professor Harvey A. Carr for much helpful criticism and many suggestions.

with exceptions to be noted later. The frequency did not vary for the several subjects.

The arm was strapped to a light movable frame arranged in such a way that the only movement permitted was upward from the elbow. This frame was connected with a lever which recorded the arm movement on a revolving drum. A signal magnet registered the beginning of the stimulus, and a tuning fork of 256 d.v. traced a time line.

The apparatus for giving the stimulus was designed to secure a current which could be controlled in strength, frequency, and duration. The current from a storage battery was led through the primary coil of a small inductorium. It was interrupted 260 times a second by means of a commutator driven by a constant speed motor. In the circuit were a milliammeter and a slide rheostat, by means of which the strength of the primary current could be kept constant.

The current from the secondary coil of the inductorium was led through the solution in which the subject's fingers were immersed. This circuit was closed by an automatic sliding contact, a copper strip passing over a brass sector. The strip was driven by the constant speed motor; its speed was reduced to one-fiftieth of that of the commutator by means of a worm and gear. There were three brass sectors of different lengths, permitting the giving of stimuli of different durations. In order to measure the intensity of the secondary current a vacuum thermocouple was placed in the circuit and a d'Arsonval galvanometer connected with it.

The intensity of the stimulating current depended in part on the strength of the primary current; but even if the latter remained constant the induced current varied with changes in contact at the surface of the commutator. This factor was not entirely subject to control, but variations in the strength of the stimulating current were kept within 5 per cent.

The frequency of the current depended on the speed of the motor. This showed no measurable variation over short ? Professor Harvey B. Lemon and Mr. Barton Hoag, of the Department of Physics, very kindly assisted with the setting up of this apparatus.

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