But qualitative testing is not sufficient during the treatment of a case of diabetes. The percentage of sugar and the quantity discharged in twenty-four hours should be determined occasionally. The process is done as follows: Place 10 cubic centimeters of Fehling's solution in a porcelain capsule, and dilute it with 40 c.c. of distilled water. Fill a Mohr's burette with the urine, which, if it contain more than 1 per cent. of sugar, should be diluted with nine times its bulk of distilled water. Slowly heat the contents of the capsule to boiling, and then allow a little of the diluted urine to run in from the burette; continue the cautious addition of urine and the gentle heating until the blue color is completely removed from the Fehling's solution. To determine the exact moment at which this takes place requires a little experience, but its recognition is facilitated by carefully tilting the capsule after each addition and stirring, so that its clear white surface may be seen through the edge of the fluid and contrasted with the latter. The number of cubic centimeters of urine used should now be read off from the burette, the number of c.c. of undiluted urine calculated therefrom, and each c.c. multiplied by .005 grm. The result indicates the quantity of sugar in grams in the urine employed, whence the percentage of sugar is determined, and also the twenty-four hours' quantity, the amount of urine passed in that period being known. The Fermentation Test.--A very simple and easy method of determining the proportion of sugar is by Roberts's fermentation method, which, although not so precise as the volumetric process, is still {213} sufficiently so for clinical purposes. A small piece of German yeast or a teaspoonful of liquid yeast is added to about four ounces (120 c.c.) of the urine, which is kept lightly stopped, at a temperature of 20° to 30° C. (68° to 80° F.), for about twelve hours; at the end of this time the sugar will have been converted into alcohol and carbonic acid. The latter will have passed off, and the urine lost in weight because of the destruction of sugar; while the difference between the specific gravity before and after the fermentation indicates the number of grains of sugar per fluidounce. Thus, suppose the specific gravity before fermentation to have been 1040, and afterward 1025; there will have been 15 grains of sugar to the fluidounce, whence, again, the twenty-four hours' quantity can be calculated. If the metric system is used, each degree of specific gravity lost will correspond to .2196 grams of sugar in every 100 c.c. of urine.