THE ACTION OF SALTS 



lU 



Later studies on the effect of salt have included measures not only of sensitivity of 

 the antigen-antibody complex to flocculation by salt, but the degree of combination. It is 

 obvious that both are affected. Duncan (1934), working with agglutinin systems, showed 

 that with flagellar agglutinins the amount of antibody combining was increased by increas- 

 ing the salt concentration from 0001 N to 1-2 N ; but similar increases reduced the com- 

 bination of somatic agglutinins. The salt concentration, by determining the amount of 

 antibody combining with bacteria, influences the position of the optimum in both titrations 

 (see also Piatt 1938). Similar results were obtained by Heidelberger, Kendall and Teorell 



10'° 10" 



10 



1 



'^ 10"^ 10"^ 10"^ 

 SALT CONCENTRATION, EQUIVALENTS PER LITRE, 



Fig. 34. 



(1936) and Heidelberger and Kendall (1936) working with Type III pneumococcal poly- 

 saccharide precipitin systems. Proving first that the reduction of precipitation in high 

 salt concentration was due to reduced combination of antigen and antibody, and not 

 to the increased solubility of the antigen-antibody complex, they were able to separate 

 a fully reactive antibody, by dissociation of optimal precipitates in strong salt solutions. 

 Their results were confirmed in other systems by Marrack and Hollering (1938). The 

 relationship also held with bacteria (Heidelberger, Grabar and Treffers 1938). 



