NORMAL HJEMATOLOGY 147 



leukaemia and dropsy, varies as the amount of iron in the cor- 

 puscles. It must therefore be evident that the specific gravity of 

 the blood varies as the percentage of haemoglobin varies. By con- 

 sulting the table of Hammerschlag, given below, the percentage of 

 haemoglobin can be read for the specific gravity of the blood at once. 

 The most practical solutions to use for finding the specific gravity 

 of the blood are benzole and chloroform, because of the ease and 

 speed with which they may be used. 



TABLE OF HAMMERSCHLAG. 



Specific gravity. Haemoglobin. Specific gravity. Haemoglobin. 



.033-1.035 = 25-30 per cent. 1.048-1.050 = 55-65 per cent. 



.035-1.038 = 30-35 " " 1.050-1.053 = 65-70 " 



.038-1.040 = 35-40 " " 1.053-1.055 = 70-75 " 



.040-1.045 = 40-45 " " 1.055-1.057 = 75-85 " 



.045-1.048 = 45-55 " " 1.057-1.060 = 85-90 " 



Appliances. Specific gravity bulb or hydrometer; a quadrilateral 

 or cylindrical graduated glass tube about six inches high ; a pipette or 

 pointed glass rod; a stirring rod, and a glover's needle. 



Reagents. Those for cleaning capillary pipette, graduated tube, 

 and needle, also benzole and chloroform. 



The hydrometer is a glass tube containing mercury and air, and 

 graduated so that when placed in distilled water at room temperature 

 it reads 1.000. 



Preparation. Clean all the apparatus as usual, and make a mix- 

 ture of benzole and chloroform in the glass tube of a specific gravity 

 of about 1.060. 



Technique. Secure the blood in the usual way. Suck at least three 

 good-sized drops of blood into the pipette. Now before the blood 

 clots insert the point of the pipette into the solution and blow out one 

 or two drops of blood, but no air. If the drop of blood goes to the 

 center of the mixture and remains there after the mixture is well 

 stirred, then the specific gravity of the blood is the same as that of 

 the mixture. If the drop comes to the top it is lighter than the 

 mixture, and benzole must be added and stirred in. If the drop goes 

 toward the bottom it is heavier than the mixture, and chloroform 

 must be added. Add just a few drops of benzole or chloroform at a 

 time and stir well and test before adding more. The quickness with 

 which the test is performed depends upon the carefulness in adding 

 the benzole or chloroform and in keeping the mixture stirred. Repeat 

 the test until the same result is easily and quickly obtained. 



Precautions. The blood will stick to whatever it comes in con- 

 tact with, the sides of the graduated tube, the stirring rod, or the 

 specific gravity bulb, if they are not clean and dry. There is danger, 

 when the pipette is used to obtain the blood, of blowing small air- 

 bubbles into the drop as it is put into the solution, which will cause 

 it to float. If the mixture is lighter than the blood, the drop will go 



