THE EFFECT OF ACIDS AND THEIR SALTS ON HEAT CONTRACTION OF RAT TENDON

¹ Department of Physiology, McGill University, Montreal, Canada

By increasing the concentration of hydrogen-ions a steplike lowering of the temperature of heat-contraction in the tendon takes place. Nitric acid has more effect in lowering the temperature of heat-contraction than has hydrochloric. The action of acetic acid is intermediate between the effects of these two mineral acids.

The addition of NaCl (0.15 moles) to HCl does not modify the temperature of heat-contraction of tendon.

Sodium acetate (0.15 moles) lowers the temperature of heat-contraction below that of acetic acid alone, while calcium acetate (0.075 and 0.15 moles) lowers it still further.

The divalent salts BaCl₂ and CaCl₂, added to HCl, have a much greater action in lowering the temperature of heat-contraction than has HCl alone.

Upon varying the concentration of salt, keeping the pH at 4.0 with HCl, it is found that NaCl and KCl up to a concentration of 0.6 moles do not affect the temperature of heat-contraction of tendon. The higher concentrations of KNO₃ (0.038 moles to 0.15 moles) inhibit the action of HNO₃.

The temperature of heat-contraction of tendon is lowered by BaCl₂ and CaCl₂ at concentrations between 0.038 and 0.062 moles. At a pH of 4.0 no difference is found in the action on tendon of the two salts in solutions of equal molar concentrations.

We take pleasure in acknowledging our debt to Mr J. K. L. MacDonald for many helpful suggestions made in the course of this investigation.