194 DETERMINATION OF SUGAR IN THE BLOOD. [BOOK f. 



reduced to coarse powder, and treated with hot alcohol ; the spirit 

 being removed, the residue is afterwards to be digested for some 

 minutes in distilled water, and raised to the boiling point ; the 

 watery solution is then filtered and evaporated to a thin syrupy 

 consistence. A drop or two of the solution, when heated on a 

 piece of porce'ain, with nitric acid and ammonia afterwards added, 

 exhibits at once the murexide test. A small portion of the same 

 solution, if acidulated strongly with acetic acid, and allowed to evapo- 

 rate spontaneously, gives rise to the crystallization of uric acid, the 

 crystals exhibiting its characteristic forms ; and lastly, the syrupy 

 solution, if merely allowed to evaporate without the addition of 

 any acid, exhibits upon its surface, after a few hours, small white 

 tufts of acicular crystal of urate of soda; the nature of the base 

 being determined by the examination of the white alkaline ash left 

 after incineration ; the acid by the murexide and other tests." In 

 cases where the amount of uric acid w r hich separates on acidulating 

 the aqueous solution in the above process by acetic acid is consider- 

 able, it may be collected on a weighed filter, washed, dried, and weighed. 

 " In the clinical examination of the blood, this process would be 

 too elaborate and tedious; but a method which answers admirably for 

 practical purposes is, to put about two drachms of the serum in 

 a flat glass dish, somewhat larger than a watch-glass, acidulate 

 slightly with acetic acid, and having placed in the fluid an ultimate 

 fibre from a piece of linen cloth (unwashed huckaback answers 

 well) set it aside in a safe place until the evaporation has proceeded 

 sufficiently far to cause it to become of a gelatinous consistence. 

 If there is uric acid in any abnormal quantity in the serum, 

 the fibre becomes studded with crystals of uric acid, which can 

 be at once recognized by placing the glass under the microscope 

 with a low power, or by the use of a small magnifying glass. 

 I have never yet, after very numerous trials, failed to discover 

 uric acid in the blood of gouty patients by this method, and the 

 test has an especial advantage in only requiring the abstraction of 

 a very small quantity of so important a fluid 1 ." 



Determination of the amount of Sugar in the Blood. 



The principle upon which all methods of estimating the amount of 

 sugar in the blood are based is to dilute the blood (sometimes only the 

 serum) and to coagulate the proteid matters and haemoglobin which it 

 contains ; thereafter to determine the sugar in the filtrate by one of 

 the methods to be described in detail under the head of Urine. The 

 following method of separating the proteid matters is that which has 

 been followed by Dr Pavy 2 in his researches. 



1 Garrod, Article "Gout," Eeynolds's System of Medicine, Vol. i. p. 825 and 826. 

 See also Garrod, Med. Chir. Transactions, Vol. xxxvu. (1854) p. 826. 



2 Pavy, "The Croonian Lectures, on certain points connected with Diabetes." 

 London, 1878. 



