88 APPLIED IMMUNOLOGY 



time to time for the occurrence of bacteriolysis. Pas- 

 sively immunized animals may also be employed for 

 the observation of Pf eiff er's phenomenon. That is, the 

 reaction will occur on injection of a mixture of cholera 

 immune serum and a culture of cholera spirilla into the 

 guinea-pig. This phenomenon can also be observed in 

 vitro, by mixing immune serum and bacteria in a test- 

 tube, and incubating at 37° C. for some time. 



What has been said of bacteriolysins regarding the 

 manner in which they operate, applies likewise to 

 cytolysins and haemolysins. Thus, for example, if a 

 specific immune serum, which has been prepared by 

 injecting the blood-corpuscles of a sheep into the peri- 

 toneal cavity of a rabbit, is mixed with the corpuscles 

 of the sheep, and incubated at 37° C, the sheep's cor- 

 puscles will after a short time be dissolved (haemoly- 

 sis). If the rabbit's serum be previously heated to 

 56° C. for half an hour, haemolysis will not take place 

 because the complement or non-specific factor in the 

 reaction will have been destroyed. The immune serum, 

 though it still retains its specific factor or hsemolysin 

 (amboceptor), has been inactivated. The serum can 

 be re-activated by the addition of fresh normal serum 

 of any animal, thus supplying complement, after 

 which the hsemolytic action will take place as before. 



In the reaction by antibodies belonging to the 

 third order of Ehrlich, whether they be bacteriolytic, 



