CHANGES OF ELECTRICAL CONDUCTIVITY IN THE BEATING TORTOISE VENTRICLE

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Abstract
A method is described for continuously recording changes in electrical conductivity. It is found that, an increase in the permeability of the tissue is associated with the systole of the tortoise ventricle beating isometrically. This increase commences at approximately the same time as the rise in intraventricular pressure. The maximum increase in conductivity bears a variable relation to the peak of intraventricular pressure occurring usually somewhat later, but occasionally shortly before the latter. During diastole the conductivity decreases. This change continues in diastasis, when the heart is mechanically quiescent. The greatest change in conductivity during a single beat is approximately 10% of the total resistance of the ventricle. Observations on the isotonic contraction are complicated by volume changes involving variations in the thickness of the ventricular wall.