But these facts hold not only for the poisonous effects of a pure NaCl solution, but also for the poisonous effects of solutions of other salts, of univalent kations with univalent anions - LiCl, KC1, NH4C1. From these experiments, then, the general conclusion may be drawn that a small amount of a bivalent kation suffices to annihilate the poisonous effects of the pure solution of a salt composed of a univalent kation with a univalent anion. It has been further shown that a trivalent kation may at will be substituted for the bivalent kation, and that a much smaller amount of a trivalent kation (Cr, Al) suffices to annihilate the poisonous effects of a pure sodium chloride solution than is required of the bivalent kation. Finally, a quantitative relation exists between the amount of the toxic salt and the amount of a bivalent kation necessary to annihilate its poisonous effects. With an increase in the concentration of the pure NaCl solution there is a corresponding increase in the minimal amount of the bivalent kation necessary to do away with its toxic effects.

These facts are of the greatest biological significance and of the most wide-spread applicability. A preliminary note announces that the valency and possibly the electrical charge of ions influence in a similar way the toxic effects of pure salt solutions upon muscle. The effect of a calcium salt in overcoming the poisonous effects of a pure sodium chloride solution upon the rhythmical contraction of a heart muscle strip becomes at once intelligible as a specific instance of the above-mentioned general law.

Loeb's experiments give us an insight, moreover, into the method by which ions possibly influence protoplasm. Some time ago he pointed out the fact that in dealing with the properties of protoplasm we are dealing, in the main, with the physics of a colloidal solution in which are dissolved certain salts. The experiments of Hardy have demonstrated most clearly the influence of the electrical charge of ions upon the physical state of colloidal particles. It requires a large amount of a univalent ion to cause the coagulation of a colloid, but a small amount of a bivalent, or a still smaller amount of a trivalent, ion will accomplish the same purpose. Loeb believes that similar facts may possibly underlie the toxic and antitoxic effects of the salts. If the electrical charge determines the antitoxic effects of a kation, then it becomes at once apparent why a small amount of a bivalent, or a still smaller amount of a trivalent, positively charged kation suffices to neutralize the poisonous effects of a pure sodium chloride solution.

The theory of electrolytic dissociation is only one of the many developments of physical chemistry that promises much if applied to the problems of pharmacology or the biological sciences in general. We must attribute a large part of our present ignorance concerning the general laws that underlie the action of drugs to the failure to recognize and utilize the fruits of this new science Innumerable papers still appear in which the physiological, pathological, and pharmacological effects of percentage solutions of various electrolytes are compared. Only chemically equivalent solutions can be compared. It is to such violations of the simple laws of physical chemistry that many of the erroneous results obtained in the biological sciences are to be attributed.

The action of electrolytes must be analyzed into the action of their constituent ions. Ultimately we shall have a classification of the electrolytes based upon the action of the ions contained in them. Once we grasp the notion that the activity of a given substance is determined by the ions it yields upon solution we shall, perhaps, find a method of rearranging our system of dosage upon this basis - a process analogous to the regulation of the dosage of crude drugs based upon their alkaloid content.