6i8 SCIENCE PROGRESS. 



a mixture of cholera vibrios together with a small quantity 

 of serum from an animal immunised against cholera into 

 the peritoneal cavity of a normal animal. By withdrawing 

 drops of fluid from the abdomen at different intervals it can 

 be seen that the micro-organisms first lose their motility, 

 then become transformed into spherules and finally dis- 

 appear. The rapidity and completness of the reaction 

 depends on various factors {e.£:, potency of serum, extent 

 of dilution, etc.). It is not so easily performed with 

 typhoid bacilli. 



Pfeiffer thouo-ht vital action essential, but Bordet found 

 that the same phenomena could be observed outside the 

 body if the temperature were kept at 37^C. He generally 

 performed the reaction with a mixture of bacilli, " im- 

 mune " ^ and normal serum, but he recognised that it could 

 occur well with only "immune" serum, and also, although 

 generally more feebly with only normal serum from various 

 sources. Bordet laid chief stress on the granular de- 

 generation of the micro-organisms rather than on the 

 agglomeration into groups. 



Durham and Gruber examined the phenomena much 

 more thoroughly, and extended it to several kinds of mi- 

 cro-organisms. They found that the addition of a small 

 quantity of "immune" serum to an emulsion of the cor- 

 responding bacillus in a test tube caused a precipitation of 

 the bacilli in the form of fine granules, the supernatant 

 liquid becoming clear. In fact the reaction resembled an 

 ordinary chemical reaction occurring slowly. A control 

 tube containing only bacilli would remain uniformly turbid. 

 The rapidity and completeness of the reaction were found 

 to depend on the same causes as in Pfeiffer's reaction. If 

 the same experiment is performed with smaller quantities 

 so that the process can be observed microscopically, under 

 suitable conditions the following stages are seen. The 

 bacilli at first isolated and moving rapidly about and across 

 the field gradually slow down and begin to hang on one 



^ For the sake of brevity, ''immune," "typhoid," "cholera," etc., 

 serum will be used ibr the serum of an immunised animal, for the serum 

 of an animal immunised against cholera, typhoid, etc., respectively. 



