NORMAL H^MATOLOGY 137 



COLORED DILUTING SOLUTION. 



Methyl violet 0.025 gram. 



Sodium chloride ....... 1.000 gram. 



Distilled water 100.000 c.c. 



Count the red cells in a group of thirty-six spaces first, and keep 

 the record as before. Next count the white cells in all of the nine 

 square-millimetre spaces and keep the record as before. This should 

 be repeated until at least two groups of red cells and three or four 

 groups of white cells are counted from different specimens on the 

 counter, and each record should be kept so that the average may 

 be taken and the number per cubic millimetre be estimated in each 

 case. 



Estimate the number of cells by taking the average and estimating 

 the number just as when counting the red cells alone. Estimate the 

 number of white cells just the same as before by taking the average 

 for each -^ c.mm., but multiply that by 100 in this case instead of 

 10 or 20, as the blood in this specimen was diluted 100 times. 



D. Centrifugalization of the Blood. To Determine the Relative 



Volume of Red Corpuscles and Plasma. To Estimate the 



Number of Red Corpuscles from Their Volume. 



Appliances. Electric or hand hsematocrit (Fig. 67) ; small rubber 

 tubing to fit capillary tube; glover's needle; white paper; fine wire 

 for cleaning tubes. 



Reagents. Distilled water, hydrogen peroxide, alcohol, and ether. 



Preparation. Adjust rubber to capillary tube. Put empty tube 

 in one arm of cross-piece to preserve balance. Use fine wire to 

 remove blood from the capillary tube, then clean and dry as other 

 tubes. 



Technique. Obtain blood from the lobe of the ear as heretofore 

 described. Draw capillary tube full of blood. Remove the rubber 

 tube by pushing it off and not by pulling. Remove any blood from 

 the outside of the capillary, and make a record of the amount of 

 blood in the capillary. Place the tube in the cross-piece of the 

 instrument as quickly as possible and centrifugalize at least three 

 minutes at the rate of 7000 to 10,000 rotations per minute. Take out 

 the tube and lay on a piece of white paper to read the divisions. 

 Each degree of the scale is estimated to contain about 100,000 cells; 

 hence, a tube in which the red column stands at 50 would indicate 

 about 5,000,000 red corpuscles per cubic millimetre. The use of 

 this instrument is designed, however, chiefly to show the volume of 

 red corpuscles rather than the number. 



Precautions. Do not displace the rubber pads in the outer ends 

 of the rotating arm, as the blood will be thrown out of the tube and 



