The antagonistic action of calcium upon the inhibitory effect of magnesium

Calcium and magnesium are chemically closely related elements. They are also close companions in the tissues of the animal body. It is the prevailing view that the physiological effect of both elements is similar in character. Many physiologists are at present of the opinion that calcium as well as magnesium exerts an inhibitory influence in the functions of the animal body. Loeb published in 1899 his observations of the inhibitory action of calcium upon the twitchings of frog muscles brought on by solutions of sodium chloride. It was then assumed by Loeb that all the members of the group of alkali earths possess inhibitory properties including at first even barium. In the numerous subsequent papers by Loeb and his pupils the discussion turned, however, essentially around the inhibitory effect of calcium. Outside of the effect of calcium upon the heart, with reference to which Howell and his followers insist, contrary to the teachings of Loeb and his school, that calcium is an exciting and not an inhibiting agent, the opinion is now widely accepted that calcium is an inhibiting factor in the animal organism. It found its way also into pathology. For instance, a number of German and Italian writers hold the view that tetany of children is due to a diminution of the calcium content of the brain.

As to magnesium we have within the last few years published several studies in support of the hypothesis that magnesium salts favor inhibitory processes. The first fact which gave rise to that hypothesis was demonstrated in 1899 to the American Physiological Society when an intracerebral injection of a few drops of a solution of magnesium sulphate caused a state of paralysis in a rabbit while the injection of other solutions brought on convulsions.