A text book of physiology . form, constituting thelatent period, and occupying on an average about x^th sec. Thetime taken up by the latent period varies somewhat according tocircumstances. 3. The shortening of the muscle up to a maximum, occupyingabout jfo sec. 4. The return of a muscle to its former length, occupying about y^ sec. Both these last events vary much in duration according to circumstances1. 1 The measurements here stated are those ordinarily given. The curve describedin the previous text happened to have a rather long latent period, and the lengtheningto be of shorter instead of
A text book of physiology . form, constituting thelatent period, and occupying on an average about x^th sec. Thetime taken up by the latent period varies somewhat according tocircumstances. 3. The shortening of the muscle up to a maximum, occupyingabout jfo sec. 4. The return of a muscle to its former length, occupying about y^ sec. Both these last events vary much in duration according to circumstances1. 1 The measurements here stated are those ordinarily given. The curve describedin the previous text happened to have a rather long latent period, and the lengtheningto be of shorter instead of longer duration than the shortening. Chap, il] THE CONTRACTILE TISSUES. 47 Tetanic Contractions. If a single induction-shock be followed at a sufficiently short in-terval by a second shock of the same strength, the first simple con-traction or spasm will be followed by a second spasm, the two bearingsome such relation to each other as that shewn by the curve inFig. 6, where the interval between the two shocks was just long. Fig. 6. Tracing of a Double Muscle Curve. To be read from left to right. While the muscle1 was engaged in the first contraction (whose complete course, hadnothing intervened, is indicated by the dotted line), a second induction-shock wasthrown in, at such a time that the second contraction began just as the first wasbeginning to decline. The second curve is seen to start from the first, as does the firstfrom the base-line. enough to allow the first spasm to have passed its maximum beforethe latent period of the second was over. It will be observed thatthe second curve is almost in all respects like the first exceptthat it starts, so to speak, from the first curve instead of from thebase-line. The second nervous impulse has acted on the alreadycontracted muscle, and made it contract again just as it would havedone if there had been no first impulse and the muscle had been atrest. The two contractions are added together and the lever raisednearly double the h
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