REACTIONS BETWEEN ANTIBODIES 31 



phenomena, Ehrlich and his school invented the artificial 

 hypothesis that these poisons consist really of a mixture 

 of a great number of different poisonous and innocuous 

 substances, which combine with antitoxin. The most 

 thoroughly examined poison, that of diphtheria, contains, 

 according to Ehrlich, not less than eight such different 

 substances. Nearly every new phenomenon led him and 

 his school to invoke the presence of a new substance. 

 Owing to this circumstance the theory of Ehrlich has to a 

 great degree lost its credibility. 



The influence of the time of reaction has also not been 

 considered by Ehrlich as much as it should have been. Thus 

 for instance, Madsen and Dreyer 1 had shown that a mix- 

 ture of diphtheria-poison and its antitoxin, which is in- 

 nocuous on subcutaneous injection into guinea-pigs, kills 

 rabbits on intravenous injection- This phenomenon was 

 explained by Ehrlich 2 as due to the presence in the diph- 

 theria-poison of a substance which could kill rabbits but not 

 guinea-pigs. The recent investigations of Morgenroth 3 

 show that the whole difference is due to the different modes 

 of injection. A mixture which is innocuous to guinea-pigs 

 when injected subcutaneously may kill them when injected 

 intracardially, i.e. directly into the blood. The reaction 

 between diphtheria-toxin and its antitoxin is not completed 

 in less than a quarter of an hour, as Ehrlich supposed from 

 his subcutaneous injections into guinea-pigs; according to 

 Morgenroth 's experiments, this reaction requires several 

 hours at 20 C. to reach the equilibrium. The experi- 



1 Dreyer and Madsen: Zeitschr. f. Hygiene, 37. 250 (1901). 



2 Ehrlich: Berl. klin. Wochenschrift, Nos. 35-37 (1903). 

 8 Morgenroth: Zeitschr. f. Hygiene, 48. 177 (1904). 



