1 98 PHAGOCYTOSIS. OPSONINS AND BACTERIOTROPINS 



taken with motile bacteria and spirilla. On microscopical examination it 

 was seen that a phagocyte was in the act of taking up a spirillum, part of 

 which was engulfed by the cell while the remainder was still outside of 

 the cell and continuing its active motility. 



Not in all cases does phagocytosis of bacteria lead to destruction of the ingested 

 microbes. More recent experiments also seem to prove that simple phagocytosis of 

 bacteria must not be considered as identical with their death. Thus, the exudate 

 from cases of anthrax in which the bacilli lie within the leucocytes, can still produce 

 fatal anthrax when inoculated into animals. 



Vital Stain- A more exact understanding of the bio-chemical nature of 

 ing with phagocytic digestion has been offered by the method of vital 

 Neutral Red. staining with neutral red. 



Neutral red (used as a i per cent, solution in isotonic saline) is a chemical dye which 

 stains only dead cells and not living ones. If live bacteria and phagocytes are mixed 

 and hanging-drop preparations of these are made, and then a drop of the stain be added 

 to different preparations at [successively increasing intervals of time, the first slide 

 shows the extracellular living bacteria unstained, while of the intracellular bacteria, a 

 part remains unstained and the other colored red. 



The later the mixtures are stained, the more numerous are the intracellular red 

 stained bacteria, showing that the ingested micro-organisms remain alive for a short 

 time, and then die. The intracellular bacteria retain their stain as long as the phago- 

 cytes themselves remain alive. Later, when the phagocytes die, the formerly red 

 bacteria lose their stain. MetchnikofFs explanation of the red staining process is 

 that during the act of digestion by the phagocytes an acid ferment is liberated which 

 gives the color reaction with the neutral red. 



For many years MetchnikofFs phagocytic theory opposed the concep- 

 tion of Ehrlich and also Pfeiffer in relation to the importance of ambo- 

 ceptor and complement in the mechanism of immunity. It would be out 

 of place here to review the various experiments performed and offered on 

 each side in explanation of its standpoint. Suffice it to say that Metch- 

 nikoff denied the existence of free complement within the animal organism. 

 He moreover claimed that the complement was found normally only in 

 the phagocytes and hence called it "cytase," differentiating the two 

 phagocyte groups as "micro- and macrocytase." The "cytase" is 

 liberated when the phagocytes are broken up. The amboceptors are 

 considered as split products of the phagocytes and known by Metchni- 

 koff as "fixators." 



2. Opsonins. 



In recent years the closer agreement which has arisen between the 

 followers of phagocytic and humoral theories was made possible by the 

 fact that Denys and Leclef, Leishmann, Wright and Douglas and others, 



