It was my intention on the "Danmark Expedition" lo carry out a 

 systematic research on the blood and the changes it undergoes 

 in the arctic climate, but I was not successful; my investigations 

 proved to be fragmentary. 



Since the question of the variations in the number of white 

 blood corpuscles and of the causes of these variations is, however, 

 of great importance and as but few investigations on the number of 

 leucocytes have been made at the same time as measurements of 

 other physiological functions, which are of interest in this connec- 

 tion, there seem to be good reasons for publishing the observations 

 recorded in the following pages. 



Before discussing my own investigations, however, I may make 

 a few remarks on the method of counting the leucocytes and its 

 accuracy. 



Various endeavours have been made in recent years to deter- 

 mine the accuracy with which the leucocytes can be counted; 

 various methods have been chosen and different results have been 

 arrived at. I shall not discuss here the considerable literature which 

 has grown up round this subject, but merely mention a few of the 

 more recent papers. 



Bruhn-Fåhræus\ who used the acetic acid method, counted 

 the numbers in a series of preparations (5—8) from the same pipette 

 in order to determine the error in counting. From 35 determina- 

 tions he found the standard deviation to be < 10 ^^/o of the average 

 in 29 cases, in none was it over 121 7^'; but in only 1 case was it 

 < 3«/o. 



The author is aware, that in using this method he disregards 

 some sources of error, absence of exactness in drawing up the blood 

 and mixing fluid etc.; but he considers — and most probably with 

 right — that the errors possibly arising in this way are of subordi- 

 nate importance. He sees clearly, that an exact determination of 

 the error requires the blood-mixture to be constantly the same and 

 therefore believes that an artificial blood-mixture must be procured 

 outside the body, as it is impossible to know whether the blood 



1 Nord. med. Archiv. 1897, No. 15, p. 19—20. 



