58 IMMUNE SERA 



The influence of salts upon agglutination is in 

 a sense comparable to their action upon the pre- 

 cipitins. Joos found that antityphoid serum did 

 not agglutinate typhoid bacilli in the absence of 

 salts. For agglutination to take place he considers 

 it as necessary as the agglutinin and agglutinable 

 substance. He believes that salts play an active 

 part in the process. Bordet, on the other hand, 

 believes that the absence of salts offers only a 

 physical impediment to agglutination. Friedberger 

 does not consider that the salts act chemically, for he 

 found that agglutination took place in the presence 

 of grape sugar, asparigin, etc., in the place of salts. 



In view of the fact that the protoplasm of the 

 body and the albuminous constituents of serum 

 have a close relationship to, or really are, colloids, 

 investigators have studied certain reactions which 

 occur among the colloids with the expectation 

 that these would throw some light on the reactions 

 of protoplasm and of serums. 1 Colloids diffuse 

 very slowly and exert little or no osmotic pressure, 

 supposedly because of the large size of the particles. 

 They do not conduct electricity, but the particles 

 react to the electric current by alterations in the 

 direction of their motion (i.e., toward the positive 

 or the negative pole) and, moreover, carry electric 

 charges themselves. The features of colloids which 



1 This subject is well presented in: Pauli-Fischer, Physical 

 Chemistry in the Service of Medicine. Wiley & Sons, N. Y. 



