516 COLLECTED STUDIES IN IMMUNITY. 



tenfold whereas the L value will remain unchanged; this is Ehr- 

 lich's hypothesis. If 9 Ao the toxin molecules had lost their toxicity, 

 without there being any formation of toxoids capable of combining 

 with antitoxin, the L value would be increased ten times. If, how- 

 ever, simultaneously with the loss of 9 /i the toxicity, the fluid 

 were to lose 9 /i the reaction rapidity for antitoxin, so that the 

 constant of the reaction would be decreased 9 / 1( ), it would be found 

 that the L value would manifest itself unchanged." 



Gruber would have done better to have made some of these com- 

 paratively simple experiments himself than to advance such an 

 untenable assumption. We are here dealing with experiments 

 which constitute, in fact, the very beginning of the technique of 

 testing poisons. Thus, when in 1897 1 I formulated the law that 

 the combination of poison and antibody takes place more rapidly 

 in concentrated solutions than in weak solutions, it was as the result 

 of just such studies made on diphtheria and tetanus toxin. In these 

 studies I convinced myself that the affinity between diphtheria anti- 

 toxin and diphtheria toxin is far greater than that between tetanus 

 antitoxin and tetanus toxin. The union of diphtheria toxin and 

 its antitoxin is effected very quickly, so that at the end of five to 

 ten minutes one may be sure that complete union has taken place. 

 It is entirely immaterial whether one is dealing with fresh poisons 

 or with poisons poor or rich in toxoids. 1 shall here reproduce an 

 experiment which I have recently made because Danysz 2 insisted 

 that the neutralizing power of the diphtheria poison changes when 

 the poison is allowed to stand for some time. 



The experiment was performed with the standard serum and 

 standard toxin used in the official standardization. Both substances 

 had therefore been very accurately titrated. The mixture was 

 allowed to stand fifteen minutes and twenty-four hours and the 

 result showed that in this time not the least change had taken place 

 in the constant. In the experiments of Danysz, therefore, some 

 error has probably crept in. In any event there is no change in 

 the reaction time on the decrease of toxicity of the diphtheria toxin. 



Guinea-pig I receives 1 I. E. serum + 0.78 cc. poison (L t ) fifteen 

 minutes after mixing. It dies on the fourth day. 



Guinea-pig II receives the same mixture twenty-four hours after 

 mixing. It dies on the fourth day. 



1 Die Werthbemessung des Diphtherieheilserums,, Jena, 1897, 



2 Annales de 1'lnstitut Pasteur 1902. 



