Thus far in the discussion of uric-acid formation we have gone on the general assumption that uric-acid excretion is an index therefor. We have followed this plan in order not to make the discussion too complex, but it must now be pointed out that uric-acid formation and uric-acid excretion do not always go on parallel to each other. Uric-acid excretion depends not on uric-acid formation alone, but probably on two other conditions: First, on retention due to the difficult solubility of the substance; second, on the decomposition of uric acid, once it has been formed inside the body.
While uric acid is a difficult soluble substance and is easily precipitated from solution, under normal circumstances the factor of retention from this cause probably influences uric-acid excretion very little. Haig, it is true, in order to bolster up his theoretical conceptions when the facts contradicted them, has made a great