AGGLUTINATION OF RED BLOOD CELLS. 331 



of serum.* If we consider the serum as a negative colloid, it is 

 easily understandable how it opposes the action of positive col- 

 loids on corpuscles; it flocks these colloids as any negative colloid 

 flocks a positive one. This explanation, however, according to 

 Mangin and Henri, is not applicable in the case of negative colloids, 

 since the latter are not precipitated by serum. These authors have 

 explained the inhibiting effect of serum on the agglutinating property 

 of negative colloids as due to the opposition that the stable colloid 

 has on the flocculation of unstable colloids of the same charge by 

 means of electrolytes, which, in the case in point, are the intra- 

 corpuscular salts diffused in the fluid. As we have already seen, 

 this interpretation is based on the explanation that they have 

 given of the agglutination of red blood cells by means of colloids, 

 with which we have already dealt. 



If the hypothesis of adhesion between stable colloids (serum) 

 and unstable colloids of the same electric charge is exact, it would 

 suffice, in explaining the inhibition of agglutination of corpuscles 

 with negative unstable colloids by serum, to consider that the 

 affinity of the colloids for serum agrees with their affinity for cor- 

 puscles. The inhibition or agglutination of red blood cells by 

 serum, and the flocculation of positive colloids by serum, and the 

 non-flocculation of negative colloids and the dissociation of barium 

 sulphate would all be due to the same cause. 



CONCLUSIONS. 



1. Certain chemical precipitates agglutinate and then hemolyze 

 washed red blood cells. 



2. This agglutination is due to the direct action of these precip- 

 itates and corpuscles upon one another. 



3. It is probable that the agglutinating property of colloids 

 for corpuscles is due fundamentally to a direct interaction of these 

 two substances. 



4. Serum even in small doses prevents the agglutination and 

 hemolysis of corpuscles by precipitates. 



* This is evidently analogous with the fact that we have referred to in our first 

 article, namely, that serum inhibits the agglutination and hemolysis of red blood 

 cells by suspensions. 



