cold fat, while they get bilious with the other. The same thing applies to butter. All these things we must honestly observe, each man for himself, and we must not let our likes and our appetites, nor our prejudices, sway the conclusions of personal experience and scientific knowledge. Dr. Haig has shown us how many of our ailments are connected with excess of uric acid in the blood, and how much this excess is due to certain foods such as meat, which contains what Fischer named purine bodies. The following extract from Halliburton’s _Handbook of Physiology_ will partially explain this subject: *Origin of Uric Acid.*--Uric acid is not made by the kidneys; when these organs are removed, uric acid continues to be formed, and accumulates in the organs, especially in the liver and spleen. After extirpation of the liver in birds (in which animals uric acid is such an important katabolite) the formation of uric acid practically ceases, and its place is taken by ammonia and lactic acid, and the conclusion is therefore drawn that in these animals ammonia and lactic acid are normally synthesized in the liver to form uric acid. But in mammals this is not the history of uric acid formation; in these animals, including man, uric acid is the end-product of the metabolism of nuclein, from the bases of which it arises by oxidization. Nuclein, the main constituent of the nuclei of cells, yields on decomposition certain products called purine substances, and their close relationship to uric acid is shown by their formulæ: PURINE BASES. Purine C_{5}H_{4}N_{4} Hypoxanthine (monoxypurine) C_{5}H_{4}N_{4}O Xanthine (dioxypurine) C_{5}H_{4}N_{4}O_{2} Adenine (amino-purine) C_{5}H_{3}N_{4}NH_{2} Guanine (amino-oxypurine) C_{5}H_{3}N_{4}ONH_{2} Uric acid (trioxypurine) C_{5}H_{4}N_{4}O_{3} “Just as the ordinary protein metabolism is both exogenous and endogenous, so is it the case with nuclein metabolism. There are certain kinds of food (such as liver and sweetbread) which are rich in nuclei, and others, such as meat, which are rich in purine bases (especially hypoxanthine). The increase in uric acid excretion after partaking of such food is exogenous, and those liable to uric acid disorders should avoid such articles of diet. Other forms of diet lead to an increase of uric acid formation by increasing the number of leucocytes in the blood, and there is a consequent increase in the metabolism of their nuclei. Increase in leucocytes may, however, be present independently of diet, and in the disease known as leucocythæmia this occurs to a marked degree; in such cases uric acid formation increases. Although special attention has been directed to the nuclei of leucocytes, because these can be readily examined during life, it must be remembered that the nuclein metabolism of all cells may contribute to uric acid formation. Uric acid, which originates by metabolism, is spoken of as endogenous.”