borne out by Emil Fischer's researches in structural chemistry, which show that the intrinsic stability of chemical systems is usually such that it can not be disturbed by "intramolecular wobble," chemical change being brought about by extramolecular or catalytic influences. The mathematical treatment of catalysis gives us a deeper insight into phenomena which no one has as yet succeeded in explaining. "We have not," says Bancroft, "the first suggestion of an adequate theory of catalysis" so essential to a better understanding of chemistry and of life itself. A true theory of catalysis will enable us to solve the problem of the transmutation of the elements, of which we have already had examples in the substances derived from radium, and the recent derivation of tellurium from copper by Sir William Ramsay. The action of animal and vegetable protoplasm is probably catalytic and the chemist can now make some vegetable substances, such as indigo or alizarine, more cheaply and purely than the plants themselves do. Could we substitute inorganic catalyzers for the vegetable enzymes and ferments in all cases, we might, as Bancroft points out, duplicate everything except the plant itself. Recently Loeb has interpreted the fact that some eggs can be developed by osmotic pressure alone, while others require fertilization, by the explanation that, in the former class the nuclein synthesis, which is necessary for segmentation, is started within the nucleus as a catalytic process, one of the products of the reaction being the catalyzer itself; while eggs requiring fertilization are such that the necessary nuclein synthesis must be started by some external catalytic agency. Again catalysis is the key to the causes and treatment of infectious diseases, the toxins and antitoxins of which are probably colloidal catalytic agents. A few drops of such a colloid as cobra venom will rapidly reduce a living animal body to a definite phase of dissipated energy, as far as its vital activity (or "free energy ") is concerned, and such catalysts as colloidal metals, which Bredig has shown to act exactly like the ferments and enzymes, can themselves be "poisoned" or rendered inert by other substances, just as toxins, venoms and poisons can be neutralized by antitoxins or other antidotes. Gibbs did not discuss colloids explicitly, because substances of such indefinite or irregular formation do not admit of mathematical treatment as such, but the physics of what we know of their intimate structure is implicit in his chapters on chemical conditions obtaining at surfaces of discontinuity. Colloids are semi-solid substances, and colloidal solutions are "pseudo-solutions," being suspensions of minute, discrete particles of matter which are not true solutions, in that they obstruct the passage of light, while neither the freezing point nor the vapor tension of the solvent can be sensibly lowered. Graham thought of colloids as dynamic phases of matter, possessing internal energy, while crystalloids are static and inert. The former include reversible colloids like gelatine which, heated with warm water, will upon cooling solidify
- Loeb, Science, 1907, N. S., XXVI., 425-37.