American journal of physiology . e induction shock. It was found that a sensory stimulus applied just as the muscle wasbeginning to contract, caused an increase in the height of the con-traction (Fig. 3). At this point in the research Hofbauer ^ published experimentssimilar to my own. He used sound as the reinforcing stimulus and 1 For a full account of the double lever see Czermak, J. H. : Der electrischeDoppelhebel, Leipzig, 1871. 2 The contact screws of Czermaks lever were here reversed, the lower one (c)being the conductor; the previous description applies to the arrangement in theexperime
American journal of physiology . e induction shock. It was found that a sensory stimulus applied just as the muscle wasbeginning to contract, caused an increase in the height of the con-traction (Fig. 3). At this point in the research Hofbauer ^ published experimentssimilar to my own. He used sound as the reinforcing stimulus and 1 For a full account of the double lever see Czermak, J. H. : Der electrischeDoppelhebel, Leipzig, 1871. 2 The contact screws of Czermaks lever were here reversed, the lower one (c)being the conductor; the previous description applies to the arrangement in theexperiments to be described presently. 3 Hofbauer : Archiv f. d. ges. Physiol, 1897, Ixviii, p. 546. Reinforcement of Voluntary Muscular Contractions. 339 obtained practically the same results. In both researches the aug-mentation was particularly noticeable as fatigue set in and the con-tractions grew smaller. The most important feature noticed in my experiments was thefact that the relaxation following a stimulated contraction was de-. FlGUkE 3. One-fourth original size. Reinforcement of voluntary contraction by sensorystimuli. The sensory stimulus was applied at the breaks in the horizontal line beneaththe contractions. The load was one kilo. cidedly quicker and more complete than that following a normal orunstimulated one, even when the stimulated contraction showed nosigns of augmentation, and as Hofbauers paper fully covered theground of the augmented contractions, attention was now turned to therelaxation phenomena. Czermaks levers were now so arranged thatthe reinforcing stimulus should be made at the moment the subjectbegan to relax from a contraction. With this arrangement it wasfound that the duration of relaxation is very considerably shortenedwhen the subject is stimulated at the moment of relaxation, as theaccompanying tracings show. So marked was this phenomenon thatwhereas the average time of a whole unstimulated or normal muscle-curve was about one second, the time of
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