214 COLLECTED STUDIES IX IMMUNITY. 



4. A further proof of the correctness of our view was furnished 

 by the results of the combining experiment when the molecular con- 

 centration of the fluid medium was increased. As is well known the 

 haemolytic action of the sera is retarded and even entirely prevented 

 by an increase in the amount of salts present. 'The investigations of 

 Markl 1 have shown that under these circumstances the amboceptor is 

 bound by the red blood-cells, whereas the complement is unable to 

 take hold. 2 Through extensive investigations, not yet published, we 

 have been able to verify this. Under these circumstances, provided 

 the view developed by us is correct, it should naturally be possible 

 to prevent the blocking with complementoids by means of suitable 

 concentrations of salts. Two parallel series of tubes with guinea-pig 

 blood to which inactive dog serum had been added were therefore 

 kept at 37 C. for one hour, ammonium sulphate having first been 

 added to one of the series in the strength of 1.3%. This addition, as 

 special tests showed us, suffices to entirely prevent the haemolytic 

 .action even of large amounts (1- cc.) of active dog serum. The result 

 of the experiment corresponded exactly to our expectations. The 

 sediments of those guinea-pig blood-cells which had been treated 

 with ammonium sulphate could be complemented with guinea-pig 

 serum, whereas in the other series no solution whatever occurred. 

 (See Table V.) 



The analysis of this case furnishes the first proof by means of test- 

 tube experiments that complementoids, the inactive modifications of the 

 complements, actually exist in the inactive serum. To be sure, even 

 heretofore their existence could not appear doubtful, for, in our 

 opinion, through the possibility of producing antibodies, proof had 

 been furnished of the preservation of the complement's haptophore 

 group in the inactivated serum. 3 



1 Markl, Uber Hemmung der Hamolyse 'durch Salze. Zeitschr. f Hygiene, 

 Vol. 39, 1902. 



2 These conditions by the way, in our judgment, have no connection with 

 the osmotic conditions of the cell membrane, as Markl believes. It seems to 

 us that the action of the salts is most readily explained by assuming that the 

 increased concentration hinders the chemical union of amboceptor and com- 

 plement. That the salts can exert such an antireactive action is seen by the 

 fact pointed out by Knorr (Munch and Wochensch. 1898, Nos. 11 and 12) that 

 tetanus antitoxin and toxin are absolutely prevented from combining by the 

 addition of 10% NaCl. 



3 In view of this new confirmation I should not want to deprive the reader 

 of an exposition of the complementoid theory from the standpoint of an opponent 



