AGGLUTINATION OF RED BLOOD CELLS. 329 



intact; if we dilute the serum, not with 3 volumes of salt solution, 

 but with 3 volumes of distilled water and heat for 15 minutes to 

 100 degrees, the dissociating property of the serum for suspensions 

 is almost intact. It should be noted, however, that whereas serum 

 diluted in salt solution and heated, becomes white, serum diluted 

 in distilled water scarcely changes in color, that is to say, the al- 

 buminous substances of the serum are very incompletely coagulated. 

 This modification of the albuminous substances is indispensable, 

 then, in order to bring about a preponderating influence of the barium 

 sulphate over the tendency to remain in solution and so allow it to 

 form clumps. If we heat serum diluted in salt solution for one- 

 quarter hour to different temperatures (55 degrees, 70 degrees, 

 85 degrees and 100 degrees), we find that an agglutination 

 of barium sulphate is produced by serum heated to 85 or to 100 

 degrees, but that dissociation is produced by serum heated to 55 

 or to 70 degrees. It is to be noted that serum heated to 70 degrees 

 has not whitened perceptibly, whereas serum heated to 85 degrees 

 has become milky. 



These facts all go to show that in a mixture of barium sulphate 

 and serum either an agglutination ordissociation is produced, accord- 

 ing to the more or less marked colloidal condition of the serum 

 employed. These two very different phenomena, however, depend 

 on the same fact. The adhesion of the colloids to the suspensions 

 is just the same as the union between the suspension and blood 

 corpuscles. The agglutination of corpuscles by chemical pre- 

 cipitates and the suspension of these precipitates in serum have one 

 common explanation, although their appearance is quite different. 



It would seem to us that the existence of an adhesion between 

 serum and a suspension like barium sulphate explains the inhibiting 

 effect that the serum plays in the agglutination of corpuscles by 

 means of suspensions. This adhesion is the result, evidently, of an 

 affinity between the suspension and serum, and we need only imagine 

 that this affinity is stronger than the one between the corpuscles 

 and the suspension. The suspension, then, would choose to unite 

 with the serum rather than with the corpuscles. 



Up to the present point we have simply referred to the experi- 

 ments with suspensions, corpuscles and serum and suggested the 

 conclusions drawn from the data obtained. We should like now to 



