When increasing loads of weight are suspended from a muscle it stretches out, and as the weights are progressively removed, it returns to its original form. This property has been interpreted as elasticity. It was first strictly investigated by F. H. Weber.1 He found that, measured by the foregoing conditions, muscle has a low but perfect elasticity. He showed that, unlike inorganic but like certain organic substances, the elongation of the muscle is not proportional to the weight, and becomes less so as the weight increases. Consequently, the curve of extensibility obtained when weights are plotted on the abscissae and elongations on the ordinates is not a straight line but a curve, which Wertheimer subsequently recognized as a hyperbola. The latter quality has been examined more recently by Haycraft2 with more accurate methods and may not hold true for degrees of elongation within physiologic limits.
Weber studied the
POLLOCK LJ, DAVIS L. MUSCLE TONE: I. EXTENSIBILITY OF MUSCLES IN DECEREBRATE RIGIDITY. Arch NeurPsych. 1929;21(1):19–36. doi:10.1001/archneurpsyc.1929.02210190022002
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