76 COLLECTED STUDIES IN IMMUNITY 



by heating to 56 C., it could be reactivated either with the com- 

 plement of sheep serum or of goat serum. To begin, the exact 

 quantity of immune body was determined which would just com- 

 pletely dissolve 2 cc. of a 5% mixture of dog blood-cells when suf- 

 ficient complement was present. This dose was found to be 0.15 cc. 

 To a number of separate portions of blood mixture (each of 2 cc.) mul- 

 tiples of this dose were then added, thus, 1, 1^, 1^, If, 2, 2^, 3 times 

 the solvent dose, and the mixtures kept at room temperature for an 

 hour and frequently shaken. Since the complement was absent, 

 haemolysis could not occur. After centrifuging, the clear fluid, 

 which had the appearance of water, was again mixed with the corre- 

 sponding amount of blood (0.1 cc. of undiluted blood) and with 

 complement. 1 It was found that even the last trace of the single 

 solvent dose had disappeared from the fluid; whereas in the case 

 where double the dose had been added, the fluid still contained just 

 a solvent dose, i.e., it completely dissolved the freshly added blood- 

 cells. In this case, therefore, the blood-cells were able to combine 

 with only a single dose of the immune body. 



This, however, is not at all the general rule, for by extendiny 

 our experiments to other cases we found that there is a very large 

 variability in this binding of the immune body, and that frequently 

 a larger or smaller multiple of the solvent dose is bound. The follow- 

 ing case will illustrate the extreme in the other direction, in which 

 almost a hundred times the solvent dose of immune body was taken up 

 by the blood-cells. A rabbit had been treated with goat blood, and its 

 serum therefore contained an immune body fitting to goat blood. Nor- 

 mal guinea-pig serum served as complement and 0.2 cc. represented 

 considerably more than sufficient for 2 cc. of the goat blood mixture. 

 When this amount of complement was employed, the solvent dose 

 of the immune body for 2 cc. of the blood mixture amounted to 

 0.008 cc. On allowing 0.48 cc. (sixty times the solvent dose) to 

 act on the blood-cells in the manner previously described, and then 

 centrifuging, it was found that the clear fluid did not contain even 

 a trace of immune body. When eighty times the dose was employed 

 the clear fluid showed a very faint solvent action, corresponding to 

 about ^ to \ of a solvent dose. Not until one hundred times the dose 



1 As a counter test the blood-cells separated by centrifuge were mixed with 

 salt solution and with the complement. Those specimens in which just the 

 solvent dose (0.15 cc.) of the immune body or more was present, dissolved, 

 completely. 



