On the Rhythm of Muscular Response to Volitional Impulses in Man

DIRECT evidence of the tetanic nature of a voluntary muscular contraction has hitherto been lacking, although its discontinuity is almost universally accepted by physiologists. Enquiry into the evidence in favour of this opinion shows it to be very insufficient. Numerous observers have attempted to demonstrate the occurrence of discontinuity by means of the rheoscopic frog preparation b)ut without success1. The opinion is indeed based almost exclusively upon the sound of a semi-nmusical quality which is emitted by a voluntarily contracted muscle, this sound being supposed to give an indication of the number of successive twitches which are fused into the tetanic contraction. This conclusion appeared to be supported by the fact that the sound of a muscle corresponds with that of a vibrating metallic reed or tuning-fork which is employed to interruipt a galvanic circuit stimulating the motor nerve. But Lov4n has shown that the true explanation of this fact is entirely different from the one which has usually been accepted 2. There are indeed many reasons against accepting the muscle-sound as evidence upon this subject. For in the first place the first sound of the heart which is certainly in the main a muscular sound is very similar to