BLOOD 269 



Control Counting. Count the red corpuscles 

 in a second drop. If the result differ greatly 

 from that of the first count, the corpuscles in a 

 third drop must be counted. 



Counting the White Corpuscles. Have ready 

 a diluting solution of glacial acetic acid (one- 

 third of one per cent). This solution will make 

 the red cells invisible. Obtain a very large drop 

 of blood. By very gentle suction fill the large 

 Thoma-Zeiss pipette to the point 0.5. Keep 

 the pipette nearly horizontal, both in obtain- 

 ing the drop and in drawing in the diluting solu- 

 tion; the bottle should be tilted. Count the 

 white corpuscles in the entire ruled disc. Kepeat 

 with a second drop. Calculate the number of 

 white corpuscles in a cubic millimetre. 



ESTIMATION OF HAEMOGLOBIN 



Oxygen Capacity of the Blood ; the Colorimetric 

 Determination of Haemoglobin. 1 Haldane and 

 Smith 2 have shown that " the coloring power of 

 the blood of different mammals varies in exact 



1 HALDANE : Journal of Physiology, 1901, xxvi, pp. 497- 

 504. This experiment should be substituted for that given in 

 "Experiments for Students in the Harvard Medical School," 

 third edition, pp. 100, 101. 



2 HALDANE and SMITH : Journal of Physiology, 1900, xxv, 

 pp. 331-343. 



