But before proceeding to the more strictly biological aspect of the relationship of uric acid to gout, we must, as in the study of any other problem of metabolism, place ourselves in possession of the main facts relating to the chemistry of _protein_, and more particularly of _purin_ or _nuclein_ metabolism; for it was just this same lack of even the most rudimentary facts, especially regarding the chemistry of uric acid, that vitiated the conclusions arrived at by the earlier workers in this sphere. Disabilities of technique of necessity rendered inaccurate the results obtained by these pioneers in research, while the significance of the facts they laboriously gleaned was likewise misinterpreted. But with the advent of highly trained organic chemists, well skilled in the investigation of bio-chemical problems, a basis of accurate chemical facts was established. The story of the fate of protein and purin substances in the animal body, at one time a medley of guesses and gaps, was brought to one of relative certitude and completeness. The change involved has proved in truth revolutionary, and many the cherished shibboleth that has been ruthlessly cast aside. How vivid the light thrown upon the problems of clinical medicine by the bio-chemists! With admiration not unmingled with awe we see them laying well and truly the foundations upon which in the ultimate scientific medicine must inevitably rest. Of these the very corner stones are _chemical physiology and chemical pathology_, the rapid evolution of which is profoundly altering our conceptions of health and alike disease. Those vital processes of the organism that but yesterday we saw “as through a glass darkly,” are now in great part illumined, and the distortions wrought in them by disease made more manifest. How pregnant, too, with warning their findings! Processes that, to our untutored minds, seemed simple are revealed as infinitely complex. Through what a labyrinth must we thread our way if we would unravel the intricacies of metabolism! Intricate enough, forsooth, in health, but how much more so in disease!—for as Sir Archibald Garrod eloquently phrases it, “It is becoming evident that special paths of metabolism exist, not only for proteins, fats and carbohydrates as such, but that even the individual primary fractions of the protein molecule follow their several catabolic paths, and are dealt with in successive stages by series of enzymes until the final products of catabolism are formed. Any of these paths may be blocked, while others remain open.” It is with chastening reflections such as these that we may best approach our study of gout, that Riddle of the Ages, upon the elucidation of which so many physicians from time immemorial have expended their dialectic skill. Would that we could affirm that the bio-chemists of to-day had found the “Open Sesame!” But, alas, it is not so! The chamber is still sealed.