590 COLLECTED STUDIES IN IMMUNITY. 



on adding dead staphylococci in not too large quantity to rabbit 

 serum, that the clear fluid separated by the centrifuge was still 

 bactericidal for typhoid bacilli, but not for staphylococci. The 

 test also succeeded when done vice versa, and with staphylococci 

 and cholera, as well as with typhoid and cholera bacilli. 



By .means of the absorption test I was able to demonstrate 

 that the bactericidal substances of normal rabbit serum were 

 independent of the hsemolytic substances. Thus, on adding anthrax 

 bacilli to normal rabbit serum, and then centrifuging, it was possible 

 to remove the bactericidal power against anthrax without in any 

 way impairing the hsmolytic power of the serum for goat and 

 sheep blood-cells. 



From what has been said it will bs seen that the bactericidal 

 action which normal rabbit serum exerts on different species of 

 bacteria is found, by experiment, to be due to several distinct 

 substances in no way dependent on one another. 



In the case of another class of antibodies, the agglutinins, recent 

 investigations have shown that they too may exist preformed in 

 normal serum. Here again the question arose whether but a 

 single substance was concerned, or whether there were many 

 different substances. 



The first experiments in this direction were made by Bordet (3), 

 who studied normal horse serum. This has the power to agglu- 

 tinate cholera and typhoid bacilli. By means of the absorption 

 technique of Ehrlich and Morgenroth, Bordet found that after 

 centrifuging serum which had been saturated with one of the 

 organisms, the agglutinating power for that organism would have 

 been lost, while that for the other organism would still be present, 

 and vice versa. Subsequently Malkoff (14) reported similar results 

 with red blood-cells. He found that normal goat serum agglu- 

 tinated (without dissolving) the erythrocytes of the rabbit, 

 pigeon, and man, while the erythrocytes of other animals were 

 but little or not at all agglutinated. Furthermore, it was found 

 that there was considerable individual fluctuation in the serum 

 of different goats. Working with the goat serum, which agglu- 

 tinated the three bloods just mentioned, he found that by adding, 

 for example, pigeon erythrocytes and then centrifuging, the cen- 

 trifuged serum would have lost its agglutinating power for pigeon 

 erythrocytes, but was still able to agglutinate the other two species 

 of blood- cells. The experiment succeeded in all possible com- 



