BY R. GREIG SMITH. 67 



had published an experiment showing how common salt was 

 necessary in causing an agglutination, he failed to accentuate the 

 part played by salts. Although most writers upon the subject 

 agree in considering agglutination as a chemical phenomenon, 

 they do not understand, or at least fail to indicate, the steps in 

 the process. Were it otherwise, the recently published papers 

 upon the role of salts in agglutination would probably not have 

 been written. 



The first of these papers is by Joos,'^' who, after enumerating 

 his experiments, concluded that — 



1. No agglutination takes place when the agglutinating sub- 



stance acts upon the agglutinable substance in the absence 

 of common salt. 



2. Agglutination always occurs when the three substances are 



together, viz., the agglutinating substance, the agglutin- 

 able substance and salt. 



3. In the absence of salt the agglutinating substance is quickly 



combined with the agglutinable substance of the bacteria. 

 This combination alters their vitality in no way. 



4. There is a close relation between the relative amounts of 



substances which together bring about the phenomenon of 

 agglutination and of the obtained quantity of agglutinated 

 substance. 



5. Salt plays an active role in the phenomenon. 



6. Salt enters into the combination of the agglutinating- and 



agglutinable substance. 



7. Agglutination can occur in a salt-free medium if the bacteria 



contain salt. 



8. The "physical theory" of Bordet is untenable. 



These conclusions of Joos simply bear out the contention that 

 agglutination depends upon the flocculating action of a particular 

 salt, viz., common salt, for the reason that this was the only salt 

 with which he experimented. 



" Joos, Zeit. f. Hygiene, xxxvi., 422. 



