Perhaps the most cogent evidence of the slight toxic effects of uric acid or urates is that derived from a study of the _uric acid infarcts_ so frequently noted in infants dying within the first two weeks of birth. According to Gideon Wells, “little or no change occurs in the renal tubule as a result of these depositions, except such as can be attributed to their mechanical effect.” This same observer, discussing this question of the toxicity of uric acid, observes, “It may be safely stated that at the present time there exists no good evidence which makes it probable that uric acid is responsible for any pathological conditions whatever, except uric acid calculi, uric acid infarcts in the kidneys, and certain manifestations of gout.” His further conclusion is that uric acid possesses but a very slight degree of toxicity, and that an actual intoxication of the organism with this substance probably never occurs. Again, we have the fact that in instances of _malnutrition in children_ excess of uric acid may occasionally be found in the blood. Yet no symptoms comparable to _gout_ occur, even though uric acid _calculi_ form. Also, as has been pointed out, showers of uric acid may be present in their urine, and yet no symptoms arise, save those referable to _mechanical_ irritation of the renal or vesical tissues. Turning to experimental researches, the evidence is cumulative as to the _non-toxicity_ of uric acid. Rabbits and dogs seem quite irresponsive, either to its ingestion in large quantities in their food, or to repeated intravenous injections of 1 or 2 grammes thereof, save only that the urine showed a large increase in uric acid. Again, Ransom, of New York, found that no systemic disturbance ensued in two cases of _chronic nephritis_, following the taking by the mouth of 3 grammes of uric acid per diem for three days in succession. All that resulted was a notable increase in the uric acid output. In one case, he went further, and on the fourth day administered 6 grammes, but nothing happened. Walker Hall, with commendable devotion, took large doses of uric acid with resultant headache and malaise, which endured for some hours. But as Luff shrewdly observes, “almost any substance, however (common salt for example), will produce toxic effects if taken in very excessive quantities.” Despite his brief indisposition, Walker Hall maintains that uric acid is rather a symptom of, than the precise _materies morbi_ in gout. Nor, apparently, even in gouty subjects can aggravation of the condition be induced by intravenous injection of uric acid. Bass and Herzberg did so until the blood content of uric acid reached the high level of 10 mg., and yet no joint attack supervened. Neither, for that matter, has it been possible to establish any relationship between degrees of uricæmia and the incidence or severity of gouty paroxysms.