CALVIN B. COULTER 321 



one hand and removal of the CO2 by a stream of oxygen, on the other, 

 the values for viscosity of the blood and refractive index of the serum 

 pass through the minima. From the data already given, it appears 

 that we must interpret these minima as corresponding with the isoelec- 

 tric points of the serum and the cells, although in the lack of definite 

 values for the reaction at which these minima occurred, this conclu- 

 sion must be considered probable rather than proved. Indeed this 

 conclusion was foreshadowed by Koranyi and Bence in their interpre- 

 tation of Hober's observations^ on the migration of red cells. 



DISCUSSION. 



The effect of the addition of sodium chloride, sodium phosphate, or 

 sodium acetate upon the velocity of cells, on the alkaline side of the 

 isoelectric point at least, is a minor one. As compared with the values 

 in the absence of electrolyte the velocities are somewhat greater in 

 the presence of NaCl, and somewhat less in the presence of the other 

 salts. These variations are in all probability due to alterations in 

 the viscosity of the medium, which was not corrected for in the meas- 

 urements given in the curves. This close correspondence of values 

 is what we should expect if the cells exist at these reactions only as 

 sodium proteinate, in these experiments. 



When normal cells are washed in four or more changes of saccharose 

 solution, a very slight absorption of CO2 from the atmosphere is suf- 

 ficient to raise the H concentration to pH 4.75, at which the cells 

 agglutinate almost instantaneously. In this condition they exist most 

 nearly in the pure state, uncombined with acid or base. 



The addition of NaCl on the other hand lessens their susceptibility 

 to change in reaction. When this salt or CaClz is added the pH 

 reached is less acid for a given amount of HCl than if the cells are 

 suspended in saccharose solution alone. It is this decrease in H con- 

 centration in the presence of salt, without doubt, which carried the 

 reaction in Hober's experiments from the acid to the alkaline side 

 of the isoelectric point and thereby prevented the saturation of the 

 solution with CO2 from bringing about a positive charge on the cells. 

 The pH value for the isoelectric point is not altered, but it is attained 

 only on the addition of larger amounts of HCl. The curve for pH 



