AGGLUTINATION. 233 



bear opposite electrical charges result in sedimenta- 

 tion when they are mixed in suitable proportions. 

 Eosin and Bismarck brown, mastic and colloidal 

 ferric hydroxid (Fe(OH) 3 ), colloidal silicic acid 

 and colloidal ferric hydroxid are mixtures which 

 behave in this way. Here also the inhibiting 

 "prozone" is obtained in concentrated solutions. 



An analogy appears to exist between bacteria 

 which have absorbedTagglutinin and certain colloids 

 in that both may be agglutinated by the addition 

 of suitable electrolytes. This phase of the agglu- 

 tination of bacteria was referred to previously. In 

 a like manner "agglutinin-bacteria" and the col- 

 loids mentioned may alike be precipitated by 

 various salts (electrolytes), such as the chlorids of 

 sodium, calcium and potassium, and many others. 1 



1. Buxton and Rahe : Jour. Med. Research, 1909, xx, 113. 



