“Et tophus scaber, et nigris exesa chelydris Creta.” _Virgil, Georg._, ii., 214. The view that tophi were composed of chalk prevailed for centuries. As we see such was the conception of Virgil, and in our own country John Hunter entertained the same erroneous notion, while amongst the laity this view as to their nature is held widely even to-day as it was in the time of Dryden. “Knots upon his gouty joints appear, And chalk is in his crippled fingers found.” _Dryden, Pers._ Albeit, the term “chalk-stones” is a misnomer, as tophi, when pure, may be wholly devoid of lime. Modern analyses, too, have failed to demonstrate the presence of calcium carbonate, the essential ingredient being _urate of soda_. On the authority of Rendu, we have it that Tennant and Pierson were the first to demonstrate the presence of uric acid in gouty deposits, which discovery was later confirmed by Fourcroy and Wollaston (1797), these latter observers showing that they consisted almost exclusively of urate of soda. Subsequently to Wollaston’s day, many analyses have been conducted, by Marchand, Lehmann, Wurzer, and Langier, L’Heretier, Ebstein and Sprague. Of the various findings we append those by Marchand, Lehmann and one of later date by Ebstein and Sprague. MARCHAND’S ANALYSIS Urate of soda 34·20 Urate of lime 2·12 Carbonate of ammonia 7·86 Chloride of sodium 14·12 Animal matter 32·53 Water 6·80 Loss 2·37 ------ 100·00 ====== LEHMANN’S ANALYSIS Urate of soda 52·12 Urate of lime 1·25 Chloride of sodium 9·84 Phosphate of lime 4·32 Cellular tissue 28·49 Water, loss, etc. 3·98 ------ 100·00 ====== EBSTEIN AND SPRAGUE’S ANALYSIS Uric acid 59·70 Tissue, organic matter 27·88 Sodium oxide 9·30 Potassium oxide 2·95 Calcium oxide 0·17 MgO, Fe, P₂O₅, S Traces.