1 82 LECTURES ON IMMUNITY 



at 20 C. (as Madsen and I observed in 1902); and dried 

 toxin lost in two years on storage in a cold room (of about 

 6 C.) two-thirds of its haemolytic power. This destruction 

 is evidently of a wholly different nature from that observed 

 at 50 C., which would be entirely imperceptible at 6 and 

 20 C. respectively. In the solutions at room temperature 

 it is perhaps bacteria (e.g. Bacillus pyocyaneus} or the 

 influence of dissolved glass which cause the rapid destruc- 

 tion ; in the dried tetanolysin other slow chemical processes 

 may be responsible for the loss of haemolytic action. 



The peculiar observation is here made that during this 

 destruction the power of binding antilysin does not 

 decrease at the same rate as the haemolytic activity. 

 Sometimes no decrease of the antitoxin-binding faculty is 

 observed at all, so that solutions of lysin and antilysin, 

 that were equivalent immediately after their union, also 

 remain equivalent after the deterioration of the poison. 

 On this ground Ehrlich concluded that the lysin is trans- 

 formed into an innocuous, or nearly innocuous, modifica- 

 tion, which retains the properties of neutralisation of the 

 antitoxin characteristic of the original poison. This sub- 

 stance is termed by Ehrlich the toxoid. The toxoid not 

 only seems to be equivalent with the poison, but also to 

 possess nearly the same constant of equilibrium. And 

 even one of the reaction-products of the toxoid with the 

 antitoxin seems to be identical with one of the products 

 of the corresponding reaction of the toxin. Only in this 

 manner is it possible to explain that the neutralisation 

 curve of the attenuated toxin is very similar to that of the 

 original toxin. It may, on the other hand, be recalled that 

 the equilibrium-constant of old tetanolysin preparations 



