CONCERNING ALEXIN ACTION. 193 



to the co-action of two substances. Pfeiffer 1 furnished the first 

 observations which led to this view when, in 1895, he succeeded 

 in restoring the bactericidal power of inactivated goat serum in the 

 peritoneal cavity of a guinea-pig. Moxter 2 subsequently demon- 

 strated the presence of normal bacteriolytic amboceptors by means 

 of reactivating experiments in vitro. And according to the numerous 

 investigations of M. Neisser and Wechsberg in this Institute, all of 

 the bacteriolysins of normal sera which they investigated, are of 

 complex constitution. This is natural because in the cell-destroying 

 properties of normal serum, as in the development and increase of these 

 properties through immunization the mechanism is exactly the same 

 in principle, although, owing to the multiplicity of the reaction products, 

 the action of the latter appears more complex. 



In my investigations of the cytotoxic properties of normal serum 

 I have included the widely distributed spermotoxic function. Accord- 

 ing to the unanimous opinion of all authorities the specific spermo- 

 toxin produced by immunization consists of two substances. Thus 

 far, however, this has not been demonstrated for normal spermo- 

 toxin, and MetalnikofT 3 has regarded the impossibility of reacti- 

 vating the heated normal spermotoxic serum as an important diag- 

 nostic means to differentiate the latter from the specific immune 

 serum. In opposition to this, by means of suitable mixtures, I 

 was able, here also, to convince myself of the complex nature of the 

 normal spermotoxin. After the spermotoxic property of rabbit 

 serum for guinea-pig spermotozoa had been destroyed by heating 

 to 56 C., I was able to restore this by the addition of guinea-pig 

 or horse serum provided I mixed the inactive rabbit serum and guinea- 

 pig serum in the proportion of 3:1 or 3:2. In that case the guinea- 

 pig spermatozoa were killed after 12-15 minutes, whereas, hi the 

 control test with inactive rabbit serum or active guinea-pig serum 

 alone, the spermatozoa showed lively movements even after 1^-1 i 

 hours. The proportion of amboceptor and complement employed 

 by me is in direct contrast to that recommended for immune sera by 

 Metchnikoff and his co-workers. The reason for this will be under- 



1 R. Pfeiffer, Weitere Mittheilungen iiber die Spezifischen Antikorper der 

 Cholera, Zeitschr. f. Hygiene, XX, 1895, 



2 Moxter, Uber die Wirkungsweise der bacterienauflosenden Substanzen 

 der thierischen Safte, Centralbl. f. Bacteriol., XXVI, 1899. 



8 Metalnikoff, Etudes sur la Spermotoxine, Annales de 1'Institut Pasteur, 

 1900. 



