408 AGGLUTINATION OF RED BLOOD CELLS 



they have been brought into contact, and that if such a membrane 

 be treated with a solution of gelatin or oxyhemoglobin, for example, 

 after the surplus protein has been washed away, the isoelectric point 

 of the membrane is now that of the protein with which it has been 

 treated. 



This observation in connection with those reported here indicates 

 the importance of factors which are non-specific in the serological 

 sense in the mechanism of agglutination. 



This view of the importance of the surface conditions in agglutina- 

 tion receives further support if the H ion concentration of the interior 

 of the red cells be examined in relation to that of the fluid in which 

 they are suspended This can be done by sedimenting the cells, 

 removing the supernatant fluid and dissolving the cell sediment in 

 a small amount of distilled water. Experiments which are shortly 

 to be reported in full have shown that on the acid side of pH 7.4 at 

 least, the reaction of the interior of fresh cells in a medium of low 

 electrolyte content is maintained at a more alkaline level than that of 

 the fluid outside. The following figures give the reactions of the out- 

 side fluid and of the dissolved cells in an experiment in which agglutina- 

 tion occurred at the two most acid reactions, although not promptly : 



In numerous other experiments the suspending fluid has been brought 

 very near pH 4.8 with the appearance of immediate agglutination, 

 and the reaction of the dissolved cells found to lie between pH 7.20 

 and 6.8 if the reaction be measured within 15 minutes after the ad- 

 dition of acid. 



The ionic state of the hemoglobin must be a large factor in the 

 electric charge carried by the cell as a whole; the value pH 4.6, in the 

 suspending fluid, as the isoelectric point of red blood cells^ appears 

 thus to correspond under the conditions of the determination with a 



