1169 
substances which react specifically with immune serum which however 
do not immunize and consequently are not antigens, I propose to 
term them as haptens. 
As to the chemical composition of these haptens from the horse’s 
kidney, I obtained results from preliminary tests, which in some 
way correspond with those achieved by Wernicke and Sorperur ?). 
However, 1 was not able to prove, whether the data concerning 
the solubility of this substance might be confirmed in all points. 
If it is true that organs of different animal species, which possess 
heterogenetic antigens, contain “compounds of protein and one or 
similar haptens, it can be understood that material derived from 
quite different sources should bring about the formation of antibodies 
producing a similar effect. 
The Hague. From the R. K. Hospital Laboratory. 
1) WERNICKE en SoRDELLI. Revista del Inst. Bacteriol. Buenos-Aires Vol. IL 
p. 281 1919. 
