592 



COLLECTED STUDIES IN IMMUNITY. 



produced by immunizing rabbits, protects only against staphylolysin, 

 and not against tetanolysin. This is well shown in the paper 

 about to be published by us. So also it can be shown that a tetanus 

 antitoxin derived from a horse has a marked protective action 

 against tetanolysin, whereas the protective action against staphy- 

 lolysin is no greater than that of normal horse serum. Finally, it 

 can be shown that normal horse serum usually protects against 

 tetanolysin and staphylolysin, but not against the haemolysin of 

 normal goat serum. The last-named, it will be remembered, acts 

 on rabbit blood-cells. These hsemolytic poisons, therefore, differ 

 qualitatively from one another. 



We see, then, that the antibody present in normal horse serum 

 does not protect rabbit erythrocytes against all blood poisons, for 

 it is not able to prevent the solvent action of normal goat serum. 

 Furthermore, it will be seen from the following experiment that 

 the protective action against a number of different blood poisons 

 is not due to a single substance. The blood poisons employed 

 were tetanolysin and staphylolysin, and the serum of four normal 

 horses was tested against these quantitatively. To begin, it was 

 necessary to determine the complete solvent dose of tetanolysin 

 and of staphylolysin for one drop of rabbit blood. Then the 

 amount of horse serum which sufficed to completely neutralize 

 (inhibit) this dose was determined. The following is an abbre- 

 viated protocol of such an experiment. 



The complete solvent dose of the staphylolysin employed (14-day 

 filtered bouillon culture of staphylococcus pyogenes aureus) was 

 0.05 cc. for one drop of rabbit blood. The solvent dose of tetan- 

 olysin was 0.25 cc. 



TABLE I. 



That is to say, the number of doses of antibody contained in 

 each cubic centimeter was 



