178 INFECTION AND RESISTANCE 



^N~aCl) 44 exerts a profound action upon the activity of complement 

 is well known. Nolf 45 noted this in 1900, and the problem has heen 

 studied since that time by many investigators. Von Lingelsheim, 46 

 who studied it in connection with his work on the refutation of the 

 "osmotic" theories of immunity, showed that increasing the salt con- 

 tents of serum (KNO 3 , NaCl, K 2 HPO 3 , etc.) progressively dimin- 

 ished its bactericidal power. Hektoen and Ruediger 47 also, after a 

 very thorough study of this phenomenon, conclude that the action of 

 the salts in such cases is exerted upon the alexin or complement and 

 not upon the heat-stable sensitizers, and that it probably depends 

 upon "physicochemical" causes. However, the manner in which 

 such salt-inactivation is brought about is, to a great extent, obscure. 

 There is no visible precipitation from serum after the addition of 

 salts sufficient in quantity to weaken its action. Nothing is, as far 

 as we can tell, removed from solution, and yet there is temporary 

 inactivation which, at the same time, renders the complement fil- 

 trable, facts from which we can only surmise some physical altera- 

 tion. 



Inactivation of the complement also follows the removal of salts, 

 but here the process is accompanied by a definite chemical change in 

 that the serum globulins are precipitated. 



Studies of this process have led to important modifications in our 

 conception of the nature of alexin, since they have shown that this 

 body, formerly assumed to be single and homogeneous, may be sub- 

 divided into at least two component parts by a number of experi- 

 mental procedures. Ferrata was the first one to point this out as a 

 consequence of investigations undertaken by him primarily with the 

 purpose of determining the nature of the influence of salts upon 

 hemolytic processes. Older studies of Buchner and Orthenberger 48 

 had shown that bactericidal action was inhibited when salts were 

 removed from the medium, but the causes underlying such inhibi- 

 tion had not been made clear. Ferrata 49 found, in the first place> 

 that the absence of salts exerted no effect upon the mechanism of 

 sensitization, but that amboceptor or sensitizer became attached to 

 the cellular elements as readily when salts were absent as when the 

 reagents were suspended in normal salt solution. It was a natural 

 inference, therefore, that the failure of hemolysis, which he observed 

 in salt-free media (analogous to the similar experiences of Buchner 



44 Alexin can be preserved in the refrigerator for long periods if hyper- 

 tonic salt solution (15 to 25%) is added. It will again become active if iso- 

 tonicity is restored with distilled water. 



45 Nolf . Ann. Past., Vol. 14, 1900. 



46 V. Lingelsheim. Zeitschr. f. Hyg., Vol. 37, 1901. 



47 Hektoen and Ruediger. Journ. of Inf. Dis., Vol. 1, 1904. 



48 Buchner and Orthenberger. Archiv f. Hyg., Vol. 10, 1C90. 

 49 Ferrata. Berl. Jcl Woch., 1907, No. 13. 



