MECHANISM IN INFECTIONS WITH TRUE PARASITES 83 



If Schneider's experiments permit the inference that these sub- 

 stances are formed through the secretory activity of the living cells, 

 then the possibility also suggests itself that this activity may be 

 impaired or paralyzed as a consequence of bacterial action, and this 

 is what Bail actually claims for his aggressins. He has shown, 

 moreover, that the peritoneal exudate has lost its anthracoccidal 

 properties even before animalized bacteria are there demonstrable, 

 and that organisms are at this time already present in the internal 

 organs and notably the spleen. He accordingly develops the follow^- 

 ing picture of what actually happens: In consequences of the normal 

 protective forces, i. e., the phagocytic action and the secretion of 

 leukins on the part of the attracted leukocytes, the majority of the 

 injected organisms are killed off soon after their introduction. Some 

 of them escape, however, and in the internal organs and notably 

 the spleen these find a relatively safe refuge. Here they assume their 

 "animalized" (infectious) state and begin the secretion of aggressins. 

 The latter are distributed through the general circulation and also 

 reach the peritoneal cavity, where they inhibit the secretory activity 

 of the leukocytes and then furnish suitable conditions for the multi- 

 plication of any surviving bacilli that may yet be present. The 

 animal is then stripped of its entire defensive mechanism and 

 now succumbs to the generalized infection. 



That the peritoneal fluid actually contains substances which can 

 prevent the liberation of leukins, at the time of the second invasion, 

 Bail has demonstrated beyond a doubt. For, on adding peritoneal 

 exudate from an infected guinea-pig, obtained at a time when the 

 primary destruction of the bacteria has been followed by their 

 reappearance in encapsulated form, to a mixture of normal serum 

 and leukocytes, in certain definite proportions, it can be shown that 

 the bactericidal effect of the leukins is completely suspended. If 

 the cells contained in this mixture are, however, killed and simul- 

 taneously extracted by alternate freezing and heating to 56 C., 

 the resultant solution is again bactericidal, showing that the active 

 substances are not injured by the aggressin exudate, but that their 

 formation is merely impeded. The reason, then, why the cap- 

 sulated organisms can at first develop in the body of a fresh animal 

 is to be sought in the primary absence of aggressins, which only 

 develop in sufficient quantity after a certain length of time. 



When this point has been reached, the animal is void of all defen- 



