A third error of the uricacidites is to talk so glibly of the chemistry of the blood and the influence of this or that food or medicine on its chemical changes. The chemistry of blood! A subject of which the ablest physiological chemists have but touched the fringe,--is that a knot to be unloosed familiar as his garter by an amateur with a watch-glass and a thread? In his _Lehrbuch der Organischen Chemie für Mediciner_, Leipzig, 1906, Bunge observes slyly that he had "sometimes had occasion to remark in private that the less a physiologist knew about chemistry, the more irresistible was his impulse to undertake the most difficult subjects." When the uric acid amateur chemist comes to study the real poisons of the blood, he will be confronted with a problem even more intricate than uric acid, though that one is intricate enough and still unsolved. For there are "poisons in the blood," though it is improbable that uric acid is one of them. These poisons are the blood-proteins, so many that the physiologist has never counted them, so minute in quantity that no chemist has ever isolated them, so complex in structure that the ablest chemists of the world stand appalled before a molecule that contains sixty atoms of carbon,[1] so powerful that an undetermined fraction smaller than one-third of a grain will kill ten thousand guinea pigs or one hundred thousand mice, and so perfectly under control that they circulate harmlessly in the normal blood. The marvel is that any animal remains alive; and no animal would remain alive were it not for a system of protection by which these poisons are rendered harmless, usually by a slight rearrangement of the atoms in their molecule which is one of the wonders of organic chemistry. We are far from knowing just what happens when we pour acids and alkalies and foods into this witches' cauldron of blood. Rather than impudently announcing the changes that are about to take place in the blood when we administer a certain food or medicine, we should stand in reverent awe before one of the most intricate and marvelous puzzles with which nature ever challenged the chemist and the physiologist. Shall we therefore stop using acids and alkalies as medicines because we do not know each step in their mode of action? By no means. We do not know each step in the mode of action of any medicine or of our foods, either, for that matter; but we do not for that reason stop eating. We should still use the acids and alkalies for their effect on the patient as far as we can see it just as we shall still go on eating food because it nourishes us; but we shall be wise to stop talking so glibly about what we cannot see and do not yet know, the effect of those acids and alkalies on the chemistry of the blood.