The recorded increases in endogenous urinary purin are, they consider, far too great to be the outcome of the stimulation of so small a proportion of the cells of the body as those of the digestive tract. On the other hand, they do not deem it necessary to assume that the whole of the endogenous uric acid is the outcome of _nuclear_ disruption, concurring with Burian’s view, that a moiety thereof may be derived from the _hypoxanthine_ of _muscular_ tissue. ENDOGENOUS URIC ACID EXCRETION The researches of Leathes and his collaborators permit the deduction that endogenous uric acid excretion bears a definite relation to the activity of cellular processes. Given unchanged physiological conditions, _e.g._, muscular exercise, the amount of the endogenous uric acid excreted is, for the same individual, fairly _constant_, and this _irrespective of diet_; but it is not the same for _different_ individuals, even those of identical body weight. According to MacLeod, the endogenous excretion in an adult man fluctuates between 0·12 and 0·20 per cent. purin nitrogen. The average daily endogenous uric acid output of a normal adult, as stated by Walker Hall, is about 0·5 gram, while that of a gouty individual is 0·45 gram. Now Burian and Schur’s original contention was that, in a given individual on a _purin-free_ diet, the endogenous purin output was _constant_, and this despite _marked_ variations in the amount of the purin-free food digested. Recent researches, however, of Folin and of Hopkins and Hope, indicate that this dictum must be modified to this extent, viz., that although it is true that the endogenous excretion continues remarkably constant, with _moderate_ variations in the amount of purin-free food, it is not so in the presence of _marked_ variations. The subject (Hopkins and Hope), after a fast of six hours, was given a meal of bread and potatoes, and at every subsequent hour estimates were made of the amount of _urea_ and _uric acid_ excreted in the urine.