Artificial immunity against toxins 397 



soluble salt, easily recognisable by its colour and markedly toxic. 

 When non-lethal doses of this salt were injected into the peritoneal 

 cavity of the guinea-pig, there was, first a transitory fall in the 

 number of the white corpuscles in the peritoneal fluid, followed by a 

 hyperleucocytosis of the most marked character. Of the leucocytes 

 accumulated in the exudation the macrophages almost exclusively 

 seized the yellowish-red granules of the trisulphide of arsenic. 

 Very shortly, the whole of the salt injected was found within the 

 peritoneal leucocytes, and the animals in which this marked phago- 

 cytosis occurred remained in good health. The ingested granules 

 could be observed for several days in the macrophages ; but in 

 course of time, these arsenical particles were broken up into very 

 small granules and ultimately disappeared. Here, then, we have an 

 intraphagocytic solution of the trisulphide of arsenic and very pro- 

 bably a transformation of this salt into some other arsenical combina- 

 tion, innocuous to the animal. This soluble substance escapes from 

 the macrophages and is finally excreted by the urinary passages. 



Since the phagocytes ingest the trisulphide of arsenic and render 

 it innocuous, it was to be anticipated that the elimination of these 

 protective cells would lead to a fatal poisoning by doses which, under 

 normal conditions, are readily withstood by guinea-pigs. When 

 Besredka used sacs of reed-pith containing non-fatal quantities of 

 the red trisulphide and introduced them into the peritoneal cavity 

 of guinea-pigs these animals were not long in exhibiting symptoms 

 of poisoning and died at the end of a longer or shorter period, this 

 varying with the amount of poison introduced. Even when the 

 phagocytic reaction had been impaired as the result of a previous 

 injection of carmine powder, the guinea-pigs died after doses of 

 trisulphide of arsenic which, under ordinary conditions, did not kill 

 them. The phagocytes in this experiment devoured numerous grains 

 of carmine and were rendered incapable of ingesting enough of the 

 trisulphide of arsenic to save the animal. On the other hand, when 

 Besredka set up a previous accumulation of macrophages in the 

 peritoneal cavity of his guinea-pigs, he succeeded in rendering 

 these animals resistant to doses of trisulphide of arsenic that, under 

 normal conditions, were fatal. The whole of these facts converge 

 to show that the phagocytes, thanks to their power of seizing the 

 trisulphide of arsenic and of modifying it within them, exercise a 

 beneficent and immunising action on the organism of the animal. [418] 

 The analogy of the main facts concerning this protective influence 



