BACTERIOLYSIS AND ALLIED PHENOMENA 173 



menon) in a similar way. The process is described at length on 

 a subsequent page, but consists essentially in this : when bacteria 

 are acted on by an excess of amboceptor, no bacteriolysis may 

 occur, although sufficient complement is present. Gay's researches 

 on this point have not been fully published at the time of writing, 

 but he apparently thinks that soluble portions receptors may 

 pass off from the bacteria into the fluid in which the latter are 

 suspended, form a precipitate with the serum, and absorb the 

 complement. Much evidence will be required before this can 

 be established ; it might perhaps explain the phenomenon in 

 vitro, where the available amount of complement is limited, but 

 the effect is also demonstrable in the peritoneum, where we should 

 expect as much complement to be forthcoming as is required. 



There is no doubt that the discovery of the absorption of the 

 complements in serum precipitates has rendered uncertain many 

 of the deductions in the process of haemolysis which have emanated 

 from the Ehrlich school, and the whole series of phenomena 

 requires re-investigation in the light of the observations of 

 Moreschi and Gay. 



Experiments with bacteriolytic sera soon showed that, though 

 they protected against specific infections, they only did so in 

 certain doses. It is, of course, readily understandable that too 

 small an amount might be without action, but it was also found 

 that too large a dose might be equally inefficacious. Thus, Loffler 

 and Abel obtained a serum which protected against B. coli, and 

 found that when a lethal dose of this organism was given the 

 animal was only protected when it had received between 0-02 and 

 0*25 c.c. of serum, larger as well as smaller doses being equally 

 without effect. Similar results have been observed with sera 

 against cholera, dysentery, malignant oedema, and other organisms, 

 and seem to be general in dealing with bacteriolytic sera as 

 opposed to antitoxin. 



They can also be obtained in vitro, and since this was first 

 shown by Neisser and Wechsberg, the phenomenon is often called 

 after them. Their method was as follows : They worked with 

 several organisms, amongst others with V. Afetchnikovi, and with 

 the serum of a rabbit which had been immunized against this 

 organism, and had acquired strong bactericidal powers. Equal 

 amounts of a broth culture of the vibrio were placed in a series 

 of test-tubes, and to each a dose of heated immune serum was 

 added. In all cases a uniform amount of normal rabbit serum 



