318 



Dr. F. W. Pavy on the Physiology of [June 14, 



of three stages. The blood is first mixed with the sulphate of soda and 

 heated to separate the albuminous and colouring matters ; the liquid is 

 then separated and the coagulum well washed to remove all the sugar. 

 Boiling with an excess of the copper solution is next performed, and the 

 reduced oxide afterwards collected and dissolved by the agency of an 

 acid. In this solution a cylinder of platinum foil is immersed, for the 

 purpose of receiving the copper removed by means of galvanic action. 

 Weighing the platinum foil before and after the operation gives the 

 weight of the deposited copper ; and from this may be calculated the 

 amount of sugar which has effected the reduction of the cupric oxide. 

 Such is an outline of the process ; but a special description of the mani- 

 pulation is required, as success is dependent upon certain details being 

 closely followed. In the application of the process many difficulties at 

 different stages presented themselves ; but it is satisfactory to be able to 

 state that they have all been overcome, and there is reason to believe that 

 no source of fallacy now exists in any part of the operation. 



Forty grms. of sulphate of soda in small crystals are weighed out in a 

 beaker of about 200 c. c. capacity. About 20 c. c. of the blood intended for 

 analysis are then poured upon the crystals, and the beaker and its contents 

 again carefully weighed. In this way the precise weight of the blood 

 taken is ascertained. The blood and crystals are well stirred together with 

 a glass rod, and about 30 c. c. of a hot concentrated solution of sulphate 

 of soda added. The beaker is placed over a flame guarded by wire 

 gauze, and the contents heated till a thoroughly formed coagulum is seen 

 to be suspended in a clear colourless liquid, to attain which actual, boil- 

 ing for a short time is required. The liquid has now to be separated 

 from the coagulum, and the latter washed, to remove all the sugar. 

 This is done by first pouring off the liquid through a piece of muslin 

 resting in a funnel into another beaker of rather larger capacity. Some 

 of the hot concentrated solution of sulphate of soda is then poured on 

 the coagulum, well stirred up with it, and the whole thrown on the piece 

 of muslin. By squeezing the liquid is expressed ; and to secure that no 

 sugar is left behind the coagulum is returned to the beaker, and the pro- 

 cess of washing and squeezing repeated. 



The liquid thus obtained may be fairly regarded as containing all the 

 sugar that existed in the blood. From the coarse kind of filtration and 

 the squeezing employed, it is slightly turbid, and requires to be thoroughly 

 boiled to prepare it for filtration through ordinary filter-paper. A per- 

 fectly clear liquid freely runs through ; and to complete this part of the 

 operation, the beaker in use and the filter-paper are washed with the con- 

 centrated solution of sulphate of soda before referred to. 



The next step is boiliug with the potassio-tartrate of copper test solu- 

 tion. The liquid is again placed over a flame, and brought to a state of 

 ebullition. A sufficient quantity of the copper solution to leave some in 

 excess is now poured in, and, from the commencement of boiling again, 

 brisk ebullition is allowed to continue for the full space of one minute. 



