40 EXPERIMENTAL RESEARCHES 



nutritious substances for themselves, and in so 

 doing to deprive parasites of them. The oppo- 

 site condition must be due to a certain dis- 

 posing influence, and immunity of the parasites 

 must be a condition of the cause of infectivity. 

 The bacterial cells may in the same way be 

 immune against haptine substances, and may 

 withstand the action of the serum. 



Thus there exist unstable relations between 

 immunity and infection, and between parasite 

 and host, relations which may depend on the 

 most varying influences, and which lead up to 

 the phenomena of reversible action, which calls 

 for further study. 



One cannot, therefore, go to work in a one- 

 sided way when analysing and judging the 

 various forms of phenomena, but must carefully 

 consider together all the factors in question. 

 The study of every possibility will bear fruit 

 and make for an understanding of the processes 

 of infection and immunity. I believe, however, 

 that I have shown the influence exerted by 

 the haptines upon the cause of infection is of 

 great importance, not only when these are 

 viewed as destroyers of the cause of infection 

 outside the cells, but also when viewed in 

 connection with the results of their anchoring 



