60 VACCINE AND SERUM THERAPY. 



Toepfer, Keith, Bulloch and Atkin, agree with Hektoen and Wright 

 and Douglas that opsonjc action is due to the presence of hitherto 

 unknown distinct bodies. 



Before this can be accepted, however, it will be necessary to 

 repeat many of the experiments that have been made, inasmuch 

 as in England and America especially, these investigations were 

 made at a time when no distinction was made between normal 

 and immune opsonins. 



The existence of normal and immune opsonins is now quite 

 generally accepted. Neufeld in a consideration of the causes of 

 phagocytosis, states that he believes bacteria and foreign bodies 

 are only taken up by the leucocytes when the latter are stimu- 

 lated. He bases this assumption on the phagocytosis of red blood 

 cells by leucocytes, which occurs only when a special haemotropic 

 serum is present. In the haemotropic serum, according to Neu- 

 feld, the physico-chemical condition is so changed that a part of 

 the body is modified so as to serve as a stimulus or appetizer for 

 the phagocytes. Virulent organisms dissolve with greater diffi- 

 culty and give off less appetizer, and because of this there is less 

 phagocytosis of virulent organisms than of organisms with de- 

 creased virulence. Spontaneous phagocytosis, according to Neu- 

 feld, is due to changes in the cell, one of these changes accident- 

 ally stimulating the leucocytes to phagocytosis. In immuniza- 

 tion Neufeld believes a specific immune substance is produced, 

 which substance modifies bacterial or other cells so that they will 

 serve to stimulate the leucocytes to phagocytosis. Immune opso- 

 nin or bacteriotropin, as he prefers to call it, is a thermostable 

 substances which does not require complement. Normal opsonin, 

 on the other hand, is believed by Neufeld to produce its action 

 because of normal amboceptor and complement, which gently 

 dissolves bacteria and in this way stimulates the leucocytes to 

 phagocytosis. The assumptions of Neufeld are borne out by 

 numerous investigators. 



Immune opsonins resist temperatures up to 55 for one hour, 

 65 C. at times not being sufficient to destroy their action. If 

 the opsonizing action of immune serum is once lost it cannot be 

 regained by the addition of fresh complement. Muir and Martin 

 have found that inactivated immune opsonin absorbs little or no 

 complement. Because of the properties of immune opsonins, they 



