THE ELASTIC PROPERTIES OF THE BEATING TORTOISE VENTRICLE WITH PARTICULAR REFERENCE TO HYSTERESIS

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Abstract
The diastolic elasticity curves of the isolated ventricle were studied in the tortoise heart under various mechanical conditions. The elasticity of the ventricle decreased progressively in successive fillings. The decrease in elasticity was correlated with a decrease in the external work of the ventricle, indicating that a progressive decrease in elasticity was associated with spontaneous failure. Over-distention of the ventricle for a short time was followed by a marked decrease in elasticity and in external work. The work gradually increased in the course of an hr., but there was relatively little increase in the elasticity during that period. The elasticity was greater on filling the ventricle than on emptying. This phenomenon was called "elastic hysteresis." In the fresh heart, the external work was also greater on filling the ventricle than on emptying. But after over-distention, the work was greater on emptying than on filling the ventricle, especially at the higher diastolic vols. A significant decrease in elasticity was produced by relative asphyxia of the ventricle. After perfusion with oxygenated fluid, the elasticity was observed to recover. The similarity of the elastic properties of skeletal and cardiac muscle was discussed.

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