80 THE BACTERICIDAL SUBSTANCES OF THE BLOOD 



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. Upon this basis, then, 

 we may imagine that the bacteria reappear in the peritoneal cavity 

 of the animal, after this has first become almost sterile, owing to the 

 fact that isolated organisms in their immediate environment, be it 

 ever so small, have succeeded in combating the opposing leukocytes 

 through aggressin formation, and have thus locally halted the anti- 

 bactericidal action of the leukins. From this point the successful 

 overthrow of the anthracoccidal action of the latter is then only 

 a matter of extension of the sphere of influence from the now newly 

 developed, encapsulated, and aggressin-producing organisms, and thus 

 purely a question of time, unless indeed the effect of the aggressins 

 can be offset in its turn, for which purpose, however, the protective 

 substances normally present do not seem adapted. 



Bail's own experiments lend support to the explanation that has 

 just been outlined. 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 

 proportion, it will be observed that the bactericidal effect of the leukins 

 is suspended. If the cells contained in this mixture are, however, 

 killed and simultaneously 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 

 defensive measures, as the capsulated organisms which alone are 

 present are not susceptible to phagocytosis, and as bactericidal 

 substances are no longer formed, owing to the paralyzing effect of 

 the aggressin upon the leukocytes so that boundless multiplication 

 and general invasion of the body are the outcome. 



If the infection of the guinea-pig is started subcutaneously instead 

 of intraperitoneally the picture is somewhat different. In this case 



