258 PHYSIOLOGICAL CHEMISTRY. 



CLINICAL USES OF THE HEMATOCRIT. 



On the assumption that the volume occupied by the corpus- 

 cles varies with the number of cells, attempts have been made 

 to use the hematocrit in place of the cell counter. With nor- 

 mal blood cells the relation is practically constant and a volume 

 of 50 per cent in the hematocrit corresponds very closely to 

 the average 5,000,000 cells per cubic millimeter. But unfor- 

 tunately where such a simple method of making a blood cell 

 count is the most desirable it is at the same time the least reli- 

 able, since in disease the corpuscles do not always retain their 

 normal size. A factor of perhaps greater importance, how- 

 ever, is obtained by taking the ratio of the volume as found 

 by the hematocrit to the corpuscle count as made by a hemo- 

 cytometer. With undiluted blood the hematocrit may be used 

 to determine whether or not pigmentation has taken place. If 

 the corpuscles are intact a nearly colorless serum is secured; 

 a more or less reddish serum points to disintegration of the 

 corpuscles. 



THE ELECTRICAL CONDUCTIVITY OF BLOOD. 



Electrolytes. It has been found by experiment that cer- 

 tain solutions conduct the electric current while others do not. 

 Pure liquids do not conduct at all, as a rule. Thus absolutely 

 pure water, glycerol, alcohol, anhydrous sulphuric acid and 

 similar substances are practically non-conductors. Solutions 

 of many organic substances are likewise non-conductors, prac- 

 tically. The sugars, for example, belong to this class. But 

 organic acids and salts and many so-called basic bodies are, 

 like the corresponding inorganic substances, conductors. In 

 general, liquid conductors or electrolytes are compounds which 

 in solution separate or dissociate into component parts or ions 

 more or less perfectly. The mineral salts and inorganic acids 

 and alkalies are in general good conductors, as they " ionize " 

 to a considerable degree. 



Blood serum has the power of conducting the current and 



