3 I2 



PHYSIOLOGICAL CHEMISTRY 



is not uniform in either of the portions of the chamber, that one should not be used 

 for counting. If the counting must be interrupted or requires a long time a moist 

 chamber 1 should be used to prevent evaporation of the diluting fluid. The diluted 

 blood may be retained in the mixing flasks and duplicate countings obtained after 

 the lapse of twenty-four hours or more according to Biirker. 



Counting and Calculation. A mechanical stage movable in two directions is 

 indispensable. With a magnification of 320 diameters the counting is begun in 

 the left upper corner of the ruling. Proceed from left to right along one row then 

 move from right to left along the next lower row, and so on. Only the small 

 squares are used for counting (see Fig. 100) and the figures are recorded in the 

 schema 2 (see Fig. 101) in which the squares crossed by horizontal or vertical lines 

 correspond to the small squares used for counting. Usually 80 squares are counted 

 and by recording the figures in the schema the count may be verified and an idea of 



Tiefe 



0.100mm. 



C.Zeiss 

 Jena 







0.01mm. 



FIG. 102. BURKER COUNTING CHAMBER. 



the uniformity of the distribution may be formed. ^ Half of the counted squares 

 should be in the one, half in the other portion of the counting chamber. For 

 more accurate measurements more squares may be counted. 



The observer will do well not to attempt counting each individual corpuscle 

 in a square. After some practice each typical group of corpuscles will immediately 

 suggest a number. A very common form of grouping is one corpuscle surrounded 

 by four others. This should immediately suggest the number five. In this way 

 the counting will become more rapid and also more reliable. 



The calculation is very simple. The number of corpuscles in 80 squares 

 divided by 100 will give the number of millions per cubic millimeter. If, for 

 example, 536 corpuscles have been counted in 80 squares then with a dilution 

 of i : 200 the number of corpuscles per cubic millimeter is 5,360,000. Thus, 



X 4000X200 =5, 360,000 erythrocytes per cubic millimeter. More than two 

 oo 



decimal places are without significance. 



1 Biirker: Pfluger's Archiv, 118, 465, 1907. 



2 The firm of H. Laupp in Tubingen has put this schema on the market (in packs of 100). 



