THE ELASTICITY AND DUCTILITY OF MUSCLE IN THE MYOSTATIC CONTRACTURE CAUSED BY TETANUS TOXIN

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Abstract
Myostatic contracture is a condition of permanent shortening in resting muscle which persists after section of the motor nerve. It develops whenever a muscle is immobilized by section of its tendon, by paralysis of its antagonists or by fixation of the limb in a plaster cast. It also develops in the late stages of experimental local tetanus. A study of the gastrocnemius muscle of the white rat in myostatic contracture due to tetanus toxin showed not only a permanent shortening of the resting muscle but an even greater relative shortening of the individual muscle fibers. The elastic stretch of a muscle in tetanus contracture is less for a given load than the stretch of a normal muscle under the same conditions. In the early stages of tetanus contracture, the after-lengthening, after-shortening and ductility are markedly increased; but they decrease again toward normal as the muscle becomes more rigidly set in contracture. The extensibility of a living muscle in myostatic contracture caused by tetanus toxin resembles that of a muscle in rigor mortis. In both the changes in elasticity and ductility are probably related to similar changes of the physical state of the muscle fibers.

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