AGGLUTINATION 399 



red cells of other animals (man, guinea-pigs, birds etc.). Colilysin can be 

 kept for months at the ordinary temperature of the laboratory and is not 

 destroyed by heating to 120 C. for half an hour. 



Some normal serums (those of man, the horse etc.) neutralize the hsemolytic 

 property of colilysin : and an anti-colilysin can be readily produced by inoculating 

 various animals sub-cutaneously with four-day old broth cultures of the colon 

 bacillus. 



5. Vaccination and serum therapy. 



Guinea-pigs and rabbits can be immunized by repeatedly inoculating them 

 either with small doses of living and virulent organisms or with filtered 

 cultures of similar strains. Albarran and Mosny produced a very high degree 

 of immunity in dogs and rabbits by repeatedly inoculating them with small 

 doses of filtered cultures and with the filtrates derived from macerating the 

 internal organs of animals dead of a colon bacillus infection. Rodet im- 

 munized horses and sheep by inoculating them repeatedly with increasing 

 doses of living or dead cultures. 



The serum of vaccinated animals has marked immunizing properties and 

 also, to some extent, therapeutic properties. These properties are mani- 

 fested against the strains used for immunization but may be wanting against 

 strains from other sources. 



Antityphoid serum is neither prophylactic nor curative for the colon 

 bacillus. 



According to the experiments of Sanarelli and some other observers animals 

 vaccinated against the colon bacillus should be immune to both the colon and typhoid 

 bacilli, and the serum of the animals should immunize against the typhoid bacillus. 

 These results have however not been confirmed. 



6. Agglutination. 



(a) The serum of animals infected with the colon bacillus or immunized 

 against that organism, as well as the serum of persons suffering from infections 

 due to the colon bacillus, have the property of agglutinating the bacillus. 

 The agglutination reaction is always obtained with the strain producing the 

 infection, but the results are often negative if other than the infecting organism 

 be employed for the reaction, though the latter may be an authentic colon 

 bacillus. This method of diagnosis cannot therefore be relied upon. The 

 capacity of the colon bacillus to agglutinate is increased to a very marked 

 extent by sub-culturing it on artificial media (Rodet). 



(b) The colon bacillus is not agglutinated by the serum of animals vaccinated 

 against the typhoid bacillus nor by the serum of persons suffering from enteric 

 fever. But for this reaction to be of any value it is important that certain 

 precautions be observed (vide footnote on p. 389). 



All human serums whether taken from enteric fever patients or not exert 

 a slight agglutinating action on the colon bacillus when diluted five or ten 

 times. Unless this fact be borne in mind it may lead to error. All mistakes 

 may be avoided by adopting the following methods. 



Determine carefully first of all the agglutinating power of the typhoid 

 serum which is to be used in the reaction : then mix a drop of the highest 

 dilution of the serum which will definitely agglutinate the typhoid bacillus 

 with a culture of the colon bacillus. Thus, for example, if the highest dilution 

 in which a given typhoid serum will agglutinate the typhoid bacillus be 

 1-100 this dilution of the serum should be used in testing the suspected colon 

 bacillus. Under these conditions the agglutination of the colon bacillus is 

 never observed, and the serum reaction can be employed as an excellent 

 means for differentiating the two organisms provided that it be always remem- 



