Effects of calcium and magnesium salts upon the development of rigor mortis

The effects of calcium and magnesium salts were studied on rabbits, cats, guinea pigs, rats and frogs; most extensively, however, on rabbits. Effects were obtained by means of subcutaneous, intravenous or intra-arterial injections; the intravenous method being more extensively employed than the other methods. The infusions were given in solutions of M/1, M/2, M/4, or M/8 concentration. Of the calcium salts we used CaCl₂, Ca(No₃)₂ and Ca(C₂H₃O₂)₂; of the magnesium salts, MgSO₄, MgCl₂, Mg(NO₃)₂ and Mg(C₂H₃O₂)₂.

The following are the chief results. Calcium salts hasten and magnesium salts retard the development of the rigor of skeletal muscles. After treatment with calcium salts the rigor may begin twenty minutes after death, and after magnesium treatment it may not begin before the lapse of six or seven hours. In the rigor after injection of a calcium salt the extensors mostly prevail irrespective of the original position. After treatment with magnesium salts the flexors prevail or the animal remains in the original position. The degree of the final rigidity after injection of a magnesium salt is not less than after similar introduction of calcium. The release from rigor appears earlier after injection of a calcium salt than after similar treatment with a magnesium compound. The administration of curare does not retard the calcium effect but it increases moderately the delaying effect of magnesium. The strong accelerating effect of a developed strychnin tetanus is not interfered with by magnesium. But the tetanus of a strong dose of strychnin can be completely suppressed and then the delaying effect of magnesium remains unimpaired. Calcium salts also hasten the heart rigor and magnesium salts delay it.