60 J. Lindhard. 



Such figures indicate a certain system in the deviations. In 10 

 countings of the 6th and 7th drops from the same pipette I have 

 found the highest number for the 6th drop in 9 cases, in 15 coun- 

 tings of the 7th and 9th drops the highest number in the 7th drop 

 13 times, once the same number for both drops and once the high- 

 est number for the 9th drop. Owing to my small material, 2 

 measuring cells and 4 pipettes, I could not obtain a complete series 

 of drops from one pipette, nor a large number of simultaneous blood 

 samples; but by counting two drops from the same pipette I have 

 come to the result, that the number of leucocytes increases in the 

 first 4 drops, then decreases a little in the 5th and 6th drops, a 

 little more in the following 2—3 drops and then remains relatively 

 constant; but I have never found such a good agreement in drops 

 from the same pipette as in the same number of drop from different 

 pipettes. It would therefore seem as if w^e must take into account 

 a special "curve" for the pipette; and this would explain the other- 

 wise strikingly large deviations obtained by Bruhn-Fåhræus. 



In consequence of this observation I have always used a def- 

 inite drop, the 6th, in comparing the enumerations; whenever any- 

 thing happened to this drop on mounting the cell I disregarded the 

 pipette as a rule. It appears, namely, that if the pipette is laid 

 aside for a while the leucocytes sink back from the capillary tube 

 into the receiver, so that the first drop or drops taken out after- 

 wards contain too few leucocytes. Where another drop than the 6th 

 is used, this has been distinctly stated. 



If we now wish to determine the amount of accuracy which 

 the method with the above-mentioned reservation can offer, we 

 must, as maintained by Bruhn-Fåhræus, make use" of a constant 

 blood-mixture. I have made some experiments in this direction by 

 letting the blood drip from the finger into a small quantity of a 

 saturated solution of MgSO^ and a little glycerine; from this mixture 

 I filled the pipettes up to the mark I and then diluted it in the 

 usual manner with acetic acid. I was successful also in obtaining 

 a series of very constant results; but the mixture had several short- 

 comings nevertheless. Thus, I always obtained lower values after 

 the mixture had stood for some time (24 hours in a cold room), 

 and the last drops also gave too low values. The two following 

 series may be cited. 



