99 



Experiments with Serum Mixtures. 



Since we know that the immune substances are all colloid systems, 

 it is a priori not to be expected that the final haemolytic etlect of a 

 mixture of various isolytic sera should correspond witli the calculated 

 haemolytic index ; or with other words: the final effect of a combina- 

 tion of several haemolytic sera must not be simply the sum of the 

 individual eft'ects of the components, because the sera — though beiny 

 colloids of the same electric character and belonging to tlie same 

 S]pecies of animals — infiuence each other. They form colloid com- 

 pounds with new peculiarities. 



Cernovodeann and Henri* found that the haemolytic ett'ect of a 

 mixture of two different sera is more than double the calculated sum 

 of the individual efi'ects of the comi^onents. The experiments I 

 wish to communicate here were all made in the same manner, 

 namely : To 2 c.c. of the mixture 1 c.c. of defibrinated blood was 

 added. The haemolysis tests of the components and the resj)ective 

 mixtures were made under the same conditions, the same day, and 

 with the same kinds of blood. 



Thus it is possible to compare the haemolytic index of the mixture 

 as it is given by experiment with the calculated haemolytic mixture 

 index which is the quotient : 



Sum of Haemolytic Indices of Components. 

 Number of Components. 



As the mixtures were made with equal quantities of serum, the 

 calculated index gives the mathematical sum of the haemolytic effects 

 of the components. 



Example. — Three sera with the indices 0-2, 0-4: and OMi. mixed 

 together (2 c.c. each) would give a calculated haemolysis 1-2 with a given 

 quantity of blood. Since only 2 c.c. of the mixture are added to a 

 constant quantity of blood, the actual quantity of each serum is only 



^ of 2 c.c. and the calculated haemolytic index would be -^—0-4. 



' Comptes Rend. Soc. Biol., No. 11. 190.i. 



