IQO THE CYTOLYSINS 



for the determination of the haemolytic complement. In actual 

 practice these procedures are all so tedious that most of the 

 measurements of complement have been made on the latter 

 variety ; the two are believed to have the same origin, and there 

 is no reason to think that the one does not run parallel to the 

 other. Gay and Ayer employ a more direct method, adding 

 varying amounts of the serum to be tested to a definite volume 

 (0*5 c.c.) of a suspension of cholera vibrios, prepared by emulsify- 

 ing four twenty-four-hour agar cultures in 10 c.c. of normal saline, 

 and subsequently adding a sufficient sensitizing dose of serum 

 from an immunized rabbit. The action is allowed to go on for 

 one and a half hours at 37 C., films prepared, stained, and 

 examined as to the degree of the changes undergone by the 

 vibrios. They found that ^-^ c.c. of normal human serum was 

 sufficient to cause a complete Pfeiffer's reaction in 0-5 c.c. of 

 cholera emulsion tested as above, whilst when y^^ c.c. was used 

 there were distinct changes. 



The Cytolysins. 



Bordet's discovery of acquired haemolytic powers, arising from 

 the injection of foreign red corpuscles, proved the starting-point 

 of a most interesting series of researches, for it was soon shown 

 that the phenomenon was not an isolated one, but that it might be 

 produced when almost any animal cell took the place of the red 

 corpuscles. Thus, Metchnikoff in 1899 prepared a leucotoxic serum 

 by the injection of the cells from the spleen of a rat (mostly 

 lymphocytes) into a guinea-pig. The serum of the latter agglu- 

 tinated and partially dissolved the leucocytes, the lymphocytes 

 being most affected. Besredka studied the subject, and found 

 that, as in the hgemolysins, two substances one thermostable 

 (sensibilatrice or amboceptor) and one thermolabile (alexin or 

 complement) took part in the reaction. He studied the speci- 

 ficity of the substance, and found it was not sharply specialized 

 in its action to leucocytes of the animal used for the source of the 

 antigen ; it would attack those of most animals, but not man. It 

 was toxic, 3 c.c. of serum being a lethal dose. He also prepared 

 an antileucotoxin. 



The next cytolysin to be prepared (by Landsteiner, and inde- 

 pendently by Metchnikoff) was spermotoxin. This was a very 

 suitable subject for study, since its action could be readily 



