OPSONINS 157 



and rendered them mere easily taken up by the 

 phagocytic cells. He called this substance opsonin 

 and showed that it is present in normal as well as 

 immune sera. By means of absorption tests 

 modelled after those of Ehrlich and Morgenroth, he 

 showed that the opsonin has a specific affinity for 

 the bacteria and none for the leucocytes. The 

 opsonins for staphylococcus prepare only staphy- 

 lococci for the leucocytes, those for tubercle bacilli 

 only these bacteria, etc. As a result of his obser- 

 vations Wright supposes that the phagocytes play 

 only a passive role, which depends on the pre- 

 liminary action of the opsonin. 



Bacteriotropic Substances. Independently of 

 Wright, though somewhat later, Neufeld and Rim- 

 pau l of Berlin published experiments on the pha- 

 gocytic effect of immune sera. They also found 

 that in these sera there exists a substance which has 

 no direct action on the phagocytes, but which can 

 fix itself on the corresponding bacteria and so modify 

 these that they are more readily devoured by the 

 phagocytes. They call this constituent a " bacte- 

 riotropic substance." There is little doubt that this 

 bacteriotropic substance and Wright's opsonin are 

 identical. Certain differences in the effect of heat 

 are probably to be explained by the differences in 

 the quantities of these sensitizing substances in 

 normal and immune sera. 



1 Neufeld and Rimpau, Deutsche med. Wochenschrift, 1904. 



