CHAP. IV.] THE BLOOD. METHODS OF RESEARCH. 195 



" Forty grammes 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 with wire gauze, and the contents heated 

 until a thoroughly formed coagulum is seen to be suspended in a 

 clear colourless liquid, to attain which actual boiling 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 coagukim is returned to the beaker 

 and the process of washing and squeezing is 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 squeezing employed, it is slightly turbid, and requires 

 to be thoroughly boiled to prepare it for filtration through ordinary 

 filter paper. A perfectly clear liquid runs through, and to complete 

 this part of the operation the beaker that has been used and the 

 filter paper are washed with some of the concentrated solution of 

 sulphate of soda before referred to." In the solution thus obtained 

 the sugar is determined by the amount of cupric oxide which it can 

 reduce, the copper being separated electrolytically. 



v. Mering 1 merely dilutes the serum with four or five times its 

 volume of water, boils and adds dilute acetic acid in sufficient quantity 

 to cause thorough separation of the proteids in a flocculent form ; 

 the filtrate is then concentrated, and the sugar in it determined 

 either by Fehling's solution or by Sachsse's method (see 'Urine'). 



Determination of the lueight of the Moist Corpuscles contained 

 in the Blood. 



Various methods have been suggested for determining the weight 

 of the moist blood corpuscles, all of which are attended with con- 

 siderable practical difficulties. Fortunately, by a combination of the 

 processes of enumeration of the blood corpuscles and determination 

 of the amount of haemoglobin contained in the blood, information 

 is acquired which possesses as great value to the physician as 



1 v. Mering, "Ueber die Ahzugswege des Zuckers aus der Dannhohle." Archiv f. 

 Anat. u. Phyniol. 1877, p. 379 et seq. 



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