PHYSICAL METHODS IN BLOOD EXAMINATION. 263 



this interference of the proteins and obtain satisfactory values. 

 The conductivity determination coupled with a few simple 

 chemical tests gives probably a better view of the inorganic 

 combinations in the serum than would be found by an exam- 

 ination of the ash of the blood, since the ash must contain sul- 

 phur and phosphorus salts resulting from the oxidation of the 

 organic compounds of these elements. The general method 

 of calculating conductivities in a mixed fluid like the blood 

 will be discussed under the head of conductivity of the urine. 

 The information furnished by conductivity measurements is, 

 it will be seen, an extension of that furnished by the osmotic 

 pressure determinations. By a combination of the two proc- 

 esses it is possible to distinguish approximately between the 

 concentrations of several classes of molecules present, and to 

 follow variations in these concentrations rapidly. As yet the 

 clinical value of the method is somewhat uncertain, however. 



