454 APPENDIX 



D CHEMICAL EXAMINATION OF THE BLOOD 



Blood Sugar. Normally we have about 0.1% sugar, or 100 mg. in 100 c.c. of 

 blood. In diabetes we have hyperglycaemia with an increase of blood glucose 

 to twice or even eight times as much. The determination of blood sugar is impor- 

 tant in differentiating the so-called "renal diabetes" from true diabetes. In renal 

 diabetes we have a normal blood sugar content. Furthermore, the sugar in the urine 

 rarely exceeds i % and this glycosuria is not affected by variations in carbohydrate 

 intake as is the case with true diabetes mellitus. Furthermore, there are no symp- 

 toms, such as thirst, excessive polyuria, loss of weight, etc. 



The micro-method of Bang is the one used by many workers in making this deter- 

 mination. Objections to it that we have noted have been the necessity for an accu- 

 rate chemical balance for the weighing of the drop or two of blood which is taken 

 up on a previously weighed piece of filter-paper. Again the titration of the cuprous 

 chloride with N/2oo iodine solution has to be carried out with exclusion of air and 

 furthermore, the previous boiling gives changing results according to time of process. 

 In my opinion it can only be carried out accurately in the hands of an experienced 

 chemical worker. 



Myers and Fine Modification of Lewis and Benedict Method. For taking blood, 



whether for sugar or nonprotein nitrogen determination, we use the blood system 



"described under "Blood Examination." With a graduated centrifuge tube we. 



make a blue pencil mark at 2 c.c. for sugar determinations, or at 5 c.c. for nonprotein 



nitrogen ones. 



A small pinch of finely powdered potassium oxalate is dusted into the bottom 

 of the graduated centrifuge tube. As the blood drops into the tube we keep agitating 

 the tube so that the oxalate dissolves and prevents coagulation of the blood. In- 

 stead of the powdered potassium oxalate we may put i c.c. of a 2% solution of the 

 oxalate in the centrifuge tube and make a mark for the blood at the 3 c.c. or 6 c.c. 

 line. Folin uses a 2 or 5 c.c. pipette into which potassium oxalate has been dusted 

 and which is connected with the needle in the vein. 



Transfer the 2 c.c. of oxalated blood, to which has been added exactly 8 c.c. of 

 water, to a test-tube. Then add 0.2 gram of picric acid. Mix thoroughly and after 

 standing five minutes filter through small dry filter. Three c.c. of filtrate are placed 

 in a tall test-tube and i c.c. of 20% Na 2 CO 3 added. Tube is placed in boiling water 

 bath for fifteen to thirty minutes. Now cool and make volume up to 20 c.c. and 

 compare by Duboscq colorimeter with a known dextrose solution (0.1%) similarly 

 treated. 



Instead of the Duboscq or Hellige colorimeter one can use the following method 

 which is sufficiently accurate for clinical purposes. 



In a case of diabetes make up a 0.2% sugar solution instead of the 0.1% and treat 

 as above with the picric acid. Then make up accurately to 20 c.c. in a graduated 

 cylinder. Now with the 20 c.c. of yellow-colored solution from the blood in a 

 tube between the thumb and forefinger of the left hand we add to the empty 

 tube alongside the known 0.2% solution from the graduated cylinder. When the 

 colors match we read off the amount used from tfce cylinder, and calculate the 

 strength of the blood sugar tube. If i$ c.c. were required it would show that the 

 sugar of the blood equalled 0.15%. 







