THE BLOOD. 557 



sample is taken. We know ; furthermore, that certain conditions greatly 

 affect these values. Thus it is well known that when a large amount 

 of water is passed, the blood may become thickened, while inanition has 

 the same effect. Vasomotor influences also can cause changes in the 

 composition of the blood throughout the entire 'organism. More and more 

 it has become recognized that it is not always possible to draw conclusions 

 concerning the behavior of the blood as a whole from the examination of 

 a single sample. For experimental work it is naturally most satisfactory 

 to withdraw all of the blood, but when this is not possible, it is always 

 advisable to make several examinations of different samples, remembering 

 at the same time that we are dealing with only relative values. 



