. Kirkes' handbook of physiology . but to the increased tension to which the fibers, as well as theirtendons and other tissues, are subjected from the resistance ordinarily opposedto their contraction. When no resistance is offered, as when a muscle is cutoff from its tendon, not only is no hardness perceived during contraction, butthe muscular tissue is even softer and more extensible than in its ordinaryuncontracted state. During contraction in each fiber it is said that the aniso-tropous or doubly refractive elements become less refractive and the singlyrefractive more so, figure 321. Chemi
. Kirkes' handbook of physiology . but to the increased tension to which the fibers, as well as theirtendons and other tissues, are subjected from the resistance ordinarily opposedto their contraction. When no resistance is offered, as when a muscle is cutoff from its tendon, not only is no hardness perceived during contraction, butthe muscular tissue is even softer and more extensible than in its ordinaryuncontracted state. During contraction in each fiber it is said that the aniso-tropous or doubly refractive elements become less refractive and the singlyrefractive more so, figure 321. Chemical Changes in Contracting Muscle. 1. The reaction of themuscle, which is normally alkaline or neutral, becomes decidedly acid duringcontraction, from the development of sarcolactic acid. 2. The muscle givesout carbon dioxide gas and takes up oxygen. The amount of the carbon dioxidegiven out does not appear to be entirely dependent upon the oxygen taken in,and so doubtless in part arises from some other source. Muscle contracts in. Fig. 323.—Diagram of Du Bois Reymonds Non-polarizable Electrodes, a, Glass tube filledwith a saturated solution of zinc sulphate, in the end, r, of which is china clay drawn out to apoint; in the solution a well-amalgamated zinc rod is immersed and connected, by means of thewire which passes through a, with the galvanometer. The remainder of the apparatus is simplyfor convenience of application. The muscle and the end of the second electrode are to the rightof the figure. an atmosphere of hydrogen, showing that oxygen is present in fixed combina-tion. A muscle, however, contracts for a longer time in an atmosphere ofoxygen. 3. Certain imperfectly understood chemical changes occur, in allprobability connected with 1 and 2, in which glycogen is diminished, andglucose and muscle sugar, inosite, appear. The nitrogenous extractives arealso increased. Electrical Changes in Contracting Muscle. Resting muscles un-injured in the body have a uniform potentia
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