. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . contrac-tion, followed by relaxation, both of which are preceded by alatent period, during which no visible but highly importantmolecular changes are taking place. The whole change of eventsis of the briefest duration, and is termed a muscle tracing shows that the latent period occupied rather morethan Tfs second, the period of contraction proper about T^, andof relaxation ^ second, so that the whole is usually begun andended within TV second ; yet, as will be learned l
. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . contrac-tion, followed by relaxation, both of which are preceded by alatent period, during which no visible but highly importantmolecular changes are taking place. The whole change of eventsis of the briefest duration, and is termed a muscle tracing shows that the latent period occupied rather morethan Tfs second, the period of contraction proper about T^, andof relaxation ^ second, so that the whole is usually begun andended within TV second ; yet, as will be learned later, manychemical and electrical phenomena, the concomitants of vitalchange, are to be observed. In the case just considered it was assumed that the muscle THE STUDY OF MUSCLE PHYSIOLOGY. 1S7 was stimulated through its nerve. Precisely the same resultswould have followed had the muscle been caused to contract bythe momentary application of a chemical, thermal, or mechanicalstimulus. If the length of nerve between the point of stimulation andthe muscle was considerable, some difference would be observed. Fig. 175.—Diagrammatic representation of the measurement of velocity of nervousimpulse (Foster). Tracing taken by pendulum myograph (Fig. 173). The nerveof same muscle-nerve preparation is stimulated in one case as far as possible frommuscle, in the other as near to it as possible. Latent period is ab, ab. respect-ively. Difference between ab and ab indicates, of course, length of time occu-pied by nervous impulse in traveling along nerve from distant to near point. in the latent period if in a second case the nerve were stimu-lated, say, close to the muscle. This is represented in Fig. 175,in which it is seen that the latent period in* the latter case isshortened by the distance from b to &, which must be owingto the time required for those molecular changes which, occur-ring in a nerve, give rise to a contraction in the muscle to whichit belongs; in fact, we have in this me
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