BY R. GREIG SMITH. 69 



pounded the following as an explanation of the mechanism : — 



The phenomenon of agglutination is made up of two quite 



distinct phases. In the first the specific substances combine 



with the salts. The second is that in which the microbes 



modified by this combination unite into floccules. 



The first phase depends upon a chemical combination 

 analogous to the formation of double salts, or of certain 

 additive compounds. It does not depend upon a molecular 

 attraction [Juxtapposition] as in dyeing or porosity pheno- 

 mena. 



The second phase is entirely similar to a chemical precipi- 

 tate, and does not depend exclusively upon a disturbance 

 of the molecular equilibrium of the mixture, which is 

 produced by the solution of the salt. 

 These statements are vague, and we do not gather from them 

 whether the individual specific substances (agglutinating and 

 agglutinable) unite with the salts and then combine, or combine 

 and then unite — an important point. Nor do we see how the 

 microbes are modified by this combination of salt and specific 

 substance. Nor is the relation between the microbes and the 

 combined specific substance defined. Although this is an attempt 

 to explain the mechanism by bringing the phenomenon into line 

 with the formation of chemical precipitates, the mechanism itself 

 is still unexplained. That the phenomenon is different from that 

 which occurs in staining fibres, etc., may be open to doubt, for 

 Knecht (Ber. 1902, 35, 1022) has shown that dyeing depends 

 upon the formation of lakes between the colour and certain con- 

 stituents of wool and silk. 



On the whole there is a tendency in these papers to consider 

 the phenomenon in a manner that is too narrow and too indefinite 

 to be scientific. That agglutination is similar to coagulation and 

 precipitation appears to be admitted by most writers, e.g., Bordet, 

 Duclaux, Nicolle, Paltauf, Kohler and Joos; but the mechanism 

 of coagulation does not appear to be understood, or Joos would 

 probably not have emphasised the role of common salt in agglu- 

 tination, and Bordet would have mentioned the function of calcium 



