BLOOD ANALYSIS 281 



advantageous to substitute 5 c.c. of blood filtrate plus 5 c.c. of water for the usual 

 10 c.c. of blood filtrate. 



Calculation. The reading of the standard in mm. (usually 20) multiplied 

 by 1.5, 3, 4-5> or 6 (according to how much of the standard solution was taken), 

 and divided by the reading of the unknown, in mm., gives the amount of creat- 

 inine in mg. per 100 c.c. of blood. In connection with this calculation it is to be 

 noted that the standard is made up to twice the volume of the unknown, so that 

 each 5 c.c. of the standard creatinine solution, while containing 0.03 mg., corre- 

 sponds to 0.015 mg. in the blood filtrate. 



Interpretation. Normally creatinine is found in the blood to the 

 extent of 1-2 mgs. per 100 c.c. In early nephritis values of from 2-4 

 mgs. are noted, and in severe nephritis 4-35 mg. Creatinine is more 

 readily excreted by the kidneys than urea or uric acid, and any in- 

 crease of creatinine to 4 or 5 mgs. or over per 100 c.c. of blood indicates 

 a marked impairment of kidney function and a probable fatal termi- 

 nation within a relatively short time. 







5. Determination of Creatine Plus Creatinine. Principle. The creatine of 

 the blood filtrate is transformed to creatinine by heating with dilute HC1 in an 

 autoclave. The creatinine preformed and from creatine are then determined 

 together by treating with alkaline picrate as under preformed creatinine. 



PrtfCtfdwre.-r-Transfer 5 c.c. of blood filtrate to a test tube graduated at 25 c.c. 

 These test tubes are also used for urea and for sugar determinations. Add i c.c. 

 of normal hydrochloric acid. Cover the mouth of the test tube with tin-foil and 

 heat in the autoclave to i3oC. for 20 minutes or, as for the urea hydrolysis, to i55C 

 for 10 minutes. Cool. Add 5 c.c. of the alkaline picrate solution and let stand 

 for 8 to 10 minutes, then dilute to 25 c.c. The standard solution required is 10 c.c. 

 of creatinine solution in a 50 c.c. volumetric flask. Add 2 c.c. of normal acid and 

 10 c.c. of the alkaline picrate solution and after 10 minutes standing dilute to 50 c.c. 

 The preparation of the standard must of course have been made first so that it is 

 ready for use when the unknown is ready for the color comparison. The height of 

 the standard, usually 20 mm., divided by the reading of the unknown and multi- 

 plied by 6 gives the "total creatinine" in mg. 100 c.c. blood. 



In the case of uremic- bloods containing large amounts of creatinine i, 2, or 

 3 c.c. of blood filtrate, plus water enough to make approximately 5 c.c., are sub- 

 stitutes for 5 c.c. of the undiluted filtrate. 



Interpretation. Total creatinine as determined by this method gives values of 

 about 5-6 mg. per 100 c.c. for normal blood.* High values for creatine have been 

 obtained in severe nephritis. 



6. Determination of Uric Acid. 1 Principle. Uric acid is pre- 

 cipitated as silver urate directly from the blood nitrate. The uric acid 



1 The following solutions are required for uric acid determinations: 

 i. The standard uric acid sulphite solution, prepared as follows: In a 500 c.c. flask 

 dissolve exactly i gm. of uric acid in 150 c.c. of water by the help of 0.5 g. lithium carbonate. 

 Dilute to 500 c.c. and mix. Transfer 50 c.c. to a liter flask; add 500 c.c. of 20 per cent 

 sodium sulphite solution; dilute to volume and mix. Transfer to small bottles (capacity 

 200 c.c.) and stopper tightly. This standard uric acid solution keeps almost indefinitely 



