The question that now thrusts itself upon us is,—What, then, is the cause of the inflammatory phenomena which determines the eruption of tophi, and alike of the arthritic outbreaks? THE CAUSE OF THE INFLAMMATORY PHENOMENA Garrod’s discovery that uric acid was present in the blood in gout not unnaturally led to the assumption that herein lay the origin of its symptomatology, and what else than confirmatory could be the deposition of uratic deposits here and there in the body. The corollary seemed obvious that, given the presence of a certain proportion of uric acid in the blood, then gout must result. But, unfortunately, it was not so; for, lo! and behold, an excess of uric acid in the blood is in no sense pathognomonic of gout. Thus, the blood in _leukæmia_ contains a high percentage of uric acid, in some cases exceeding that found in gout, and enduring, moreover, for a longer period. Yet no symptoms distinctive of gout appear, nothing that can be referred to _uric acid_. But it was contended the reason why gout does not ensue is because simultaneously with increased formation there is increased elimination of uric acid. But, unfortunately, despite augmented excretion, the percentage of uric acid in the blood is still maintained at a high level, and still no gout occurs. Moreover, it is met with also in nephritis, simple and pernicious anæmia, intestinal inflammation, certain fevers, notably in malaria between attacks, and in typhus after the febrile stage, pneumonia, plumbism, etc. Indeed, the ubiquitousness with which uric acid is found in the blood, and this in conditions wholly distinct from gout, would of itself seem sufficient to dissipate any lingering doubts as to its being anything more than a symptom of gout and not its proximate cause. Obviously, with these revelations the uric acid theory was within measurable distance of being uprooted. Deposed from its high estate as a causal agent, and accredited with only a symptomatic value, the question arose whether indeed this bogey, “uric acid,” was even capable of fulfilling a minor _rôle_, of originating any symptoms, much less gout, in its entirety. In other words, is uric acid toxic or non-toxic? NON-TOXICITY OF URIC ACID The adherents of the uric acid theory did not hesitate to attribute to its toxic action, not only the severe phenomena of acute attacks, but even all the functional disorders of so-called _irregular_ or _visceral_ gout. By the more ardent advocates, such as Haig, we were treated to a word picture of how solid crystals of uric acid erupted out of the blood-stream, and anchoring themselves in nerve sheathes, the renal substance and the mucous membrane, gave birth to chronic neuralgias, nephritis, rhinitis, and so forth. But, alas, there is very serious doubt as to whether uric acid or the urates are capable of acting even as mechanical, much less as true _toxic_ irritants.