In other words, hampered by the above disabilities in our tests, it is beyond our power to determine whether “the increases denote a supernormal nuclein metabolism or an unusual type of nuclein cleavage.” Should it ultimately transpire that the increase in the purin blood content is a _real_ one, viz., made up of “an excess of normally formed and normally bound purins,” a great step forward will have been achieved. For, to account for the same it will, as Walker Hall observed, be necessary to postulate a _supernormal nuclear activity_ of _generalised or_ localised distribution. _Need for Further Investigations._—While none can doubt that, by means of chemical investigation of the _blood_, the clinical problem of gout will be elucidated to a much greater extent than has been possible by means of _urine analysis_, still much remains to be done before recent findings can be applied to the solution of the etiology of _gout_. The results of _blood analyses_ up to now have afforded us no clue as to the intimate nature of the warp in _nuclein metabolism_. At the most, the researches in this sphere do but make it increasingly clear that uricæmia is _not the cause but the result_ of gout. Albeit, this conclusion does not justify us in putting out of court all thought of _uric acid_ in connection with gout. Any tendency thereto will be immediately checked when we recall that uratic deposits, _i.e._, _tophi_ constitute the solitary unequivocal token of gout, and to this aspect of the question the ensuing chapter will be devoted. Meanwhile, systematic investigations of the purin content of the blood, not only in gouty but in _normal_ subjects, would surely dissipate much of the obscurity that envelops this complex question. It were well, too, that _blood_ and _urine_ analyses go hand in hand in our investigations. How illumining these have been in connection with _atophan_, the increased urinary output of uric acid having been found to be correlated with a simultaneous sinking in the level of the uric acid of the blood. Again, the _excretion of urinary purin_ ebbs and flows with the intake of food and the degree of muscular activity, while sleep also exerts an influence, not to mention constitutional disturbances, _e.g._, fever infections, etc. Can it be doubted that the _blood_ content of uric acid varies with these same vicissitudes? Walker Hall tells us that the data to hand, “as to the rapidity of the appearance of purins in the blood-stream after food, infections, fever, etc.,” though few in number, yet suggest that “the excretion by the kidney is _tidal_ in character, and that the blood uric acid has similar characteristics.” In light of these possibilities, we may well pause before attempting to appraise exactly the significance of isolated blood examinations.