PRODUCTION OF SUGAR IN THE LIVER. 301 



however, we have generally used animal charcoal. We have 

 used both methods in decolorizing the decoction of the liver- 

 substance, as well as in operating upon the blood. 



In ordinary examinations, Trommer's test is sufficiently 

 delicate ; but it is not so sensitive nor so convenient as some 

 of the standard test-solutions. We have been in the habit 

 of using, for the determination of sugar in the urine, a modi- 

 fication of Fehling's test, which is also very convenient for 

 examinations of the blood and liver-extract. This may also 

 be used for quantitative examinations ; but, like all of the 

 standard solutions, it presents the inconvenience of under- 

 going alteration by keeping, so that it is desirable to use it 

 freshly-made for each series of examinations. We have suc- 

 ceeded in obviating this difficulty, however, by the following 

 modification in its preparation ; and, made in this way, it is 

 probably the most convenient test that can be used in the 

 examination of any of the animal fluids for sugar. 



Fehling^s Test for Sugar. The modification in the test 

 consists simply in preparing three separate solutions, which 

 are to be mixed just before using, as follows : 



Solution of crystallized sulphate of copper, 90 grains in 

 an ounce of distilled water. 



Solution of neutral tartrate of potash, 36i grains in an 

 ounce of distilled water. 



Solution of caustic soda, specific gravity 1*12. 



These solutions are to be kept in separate bottles, and 

 used as follows : 



Take half of a fluidrachm of the copper-solution, add 

 half a fluidrachm of the solution of tartrate of potash, and 

 add the solution of caustic soda, to make three fluidrachms. 

 It is important to measure the copper-solution with especial 

 accuracy for quantitative analyses, as the quantity of copper 

 decomposed indicates the amount of sugar. 1 



1 The above modification of Fehling's test consists simply in making and 

 keeping the solutions separately, and mixing them for use in the proportions 



