AGGLUTINATION OF RED BLOOD CELLS. 327 



having been heated for 15 minutes in boiling water). After a few 

 minutes we again centrifugalize. 



The supernatant fluid is absolutely limpid and has no effect on 

 fresh barium sulphate and does not turn white on boiling. 



To sum up, we have seen that the dissociation of barium sul- 

 phate by serum and its agglutination by red blood corpuscles is 

 due fundamentally to the same phenomenon, namely, the adhesion 

 of the sulphate with the particles of the serum or of the corpuecles, 

 as the case may be. We have offered the hypothesis that the 

 result of such a combination depends on the tendency of the par- 

 ticles united with barium sulphate to remain in suspension, and we 

 have shown that by diminishing this tendency the property of 

 the sulphate to sediment becomes preponderant and leads to an 

 agglutination instead of a dissociation. This hypothesis is sup- 

 ported by the experiment to which reference has just been made.* 



* Two objections may be raised which it may be well to meet before going 

 farther. It might be possible that the substances causing agglutination or dis- 

 sociation with barium sulphate, in accordance with whether the serum has or has 

 not been heated, are not the same; and it might be supposed that heat has simply 

 caused the agglutinating property to appear by destroying the dissociating prop- 

 erty. Such, however, does not seem to be the case. We find that on treating 

 a certain amount of fresh serum (0.5 c.c. plus 1.5 c.c. of salt solution) with large 

 amounts of barium sulphate, we remove, as we have already mentioned, all 

 the dissociating properties of the serum. If the diluted serum treated in this 

 manner is then heated for one-quarter hour to 100 degrees with a tube of serum 

 that has not been treated with barium sulphate, the latter becomes milky through 

 coagulation of its albuminous substances, whereas the first tube shows no appre- 

 ciable whitening. The addition of this latter treated serum to a small amount 

 of barium sulphate produces little or no agglutination. By removing the disso- 

 ciating substance from fresh serum by adding large doses of sulphate, we thus 

 remove at the same time its property of agglutinating the sulphate after heating. 

 This renders it very probable that the different actions on barium sulphate are 

 due to the same substances. 



The objection may also be raised that the dissociating property of serum is 

 retained even after heating, but is masked by the agglutinating properties which 

 this heating develops. This, however, does not seem to us to be correct. We 

 have just seen that the agglutinating properties may be removed from heated 

 serum by treating it with large doses of barium sulphate, and it may also be noted 

 from the doses that we have given that this removal is much easier than the 

 removal of the dissociating property from unheated serum. Thus we find that 

 whereas 4 c.c. of our emulsion of sulphate suffices to remove the agglutinating 

 property from 2.4 c.c. of serum diluted 1-4 and heated to 100 degrees, 10 c.c. 

 of the same emulsion suffices only to weaken the dissociating properties of 2 c.c. 

 of the same serum diluted 1-4 and unheated. If the agglutinating and dissocia- 



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