. Elements of human physiology. Physiology. 116 PHYSIOLOGY The discovery of exact means of measuring the heat pro- duction during contraction was naturally utilised to determine the relation between the heat produced and the work done under varying conditions. In the muscle as in a steam engine, we have a conversion of potential energy stored up in carbon compounds into kinetic energy, which may appear as work and heat. In the engine there is a definite ratio be- tween work and lieat. Only a certain small proportion of the total energy can be utilised as work, the rest being dissipated as heat
. Elements of human physiology. Physiology. 116 PHYSIOLOGY The discovery of exact means of measuring the heat pro- duction during contraction was naturally utilised to determine the relation between the heat produced and the work done under varying conditions. In the muscle as in a steam engine, we have a conversion of potential energy stored up in carbon compounds into kinetic energy, which may appear as work and heat. In the engine there is a definite ratio be- tween work and lieat. Only a certain small proportion of the total energy can be utilised as work, the rest being dissipated as heat. The exact proportion depends on the difference of temperatures that is available in the machine, and in the best engines at our disposal amounts to one-tenth. If the machine does no work, the heat production is increased by the amount Pre. ACTIVE MUSCLE RESTING MUSCLE Diagram of the arrangement for showing the development of heat during muscular contraction. A B, B A, two thermo-electric junctions; G, galvanometer. (After Waller.) corresponding to the work. The same is true to a certain extent in muscle. If a muscle be allowed to contract and relax twenty times when loaded by a weight, the total external work done will be nothing. If however the weight be attached to the axle of a wheel, which is provided with a catch so that the weight can only be drawn up (Fig. 49), and the muscle be allowed to pull at each contraction on the circumference of the wheel, at each contraction work is done. It is found that in the latter case the muscle is less heated than in the former, and the difference is equivalent to the work done in raising the weight. But as soon as we begin to alter the work by altering the weight, we are at once met by the difficulty that increased tension augments all the properties of the muscle,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illust
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