316 



ISOELECTRIC POINT OF RED BLOOD CELLS 



more rapidly with increasing alkalinity than the charge of sensitized 

 cells. The slower movement cannot be explained by the formation of 

 agglutinated masses, since at the upper end of the curve at least no 

 agglutination appeared even after 12 hours standing in the U-tube. 

 On the acid side of the isoelectric point the measurements are not 

 numerous and probably not accurate enough for a comparison. 



The optimum H concentration for agglutination was determined by 

 titrations exactly like those described above. Varying amounts of 

 cells were used; the sharpest results were obtained by adding 1 or 2 



B 5 



o 4 



S 3 



> 



O 1 



s ^ 



5.5 



6.0 



5.5 



5.0 



4.5 



4.0 



3.5 pH 



Fig. 3. Curve showing the movement in mm. during 10 minutes of sensitized 

 red blood cells. 



cc. of 10 per cent cells to 10 cc. of saccharose solution containing 

 increasing amounts of HCl. At the optimum concentration agglutina- 

 tion is almost instantaneous; at greater and less acidities agglutina- 

 tion appears more slowly, but was practically completed within 30 

 minutes. The agglutination arranges itself asymmetrically on either 

 side of the optimal point; with normal cells it never was observed 

 at reactions more alkaline than pH 5.6, and seldom beyond pH 5.1. 

 This variation is probably connected with variations in the amount 

 of electrolyte present, and will be considered later. On the acid side 



