410 The Influence of Bacterial Endotoxins on Phagocytosis. 



the ratio of active and non-active phagocytes is at least of equal importance. 

 In these observations attention has been paid to the percentage of non- 

 phagocytic cells, the importance of which has been previously insisted upon 

 by many workers on phagocytosis. 



When the reduction of phagocytosis by endotoxins had been proved,* 

 investigations were undertaken for the purpose of ascertaining whether these 

 toxic substances were resistant to heat. It was found that they were 

 unaffected by exposure to a temperature of 60° C. for periods varying from 

 15 minutes to three hours, and that the results obtained with the heated 

 substance were identical with those obtained with the unheated, as may be 

 seen from the following experiment. 





No. of 



bacteria in 

 50 cells. 



No. of 



non-phagocytic 

 cells. 



„ „ + „ + B, typhosns 



C. Serum B. typhosus extract* + leucocytes + M. aureus 



„ . „ + „ + B. typhosus 



182 

 198 

 26 

 17 

 46 

 15 



9 

 3 

 43 

 38 

 33 

 37 



* This extract has been exposed to a temperature of 60° C. for three hours. 



The Effect of Diluting the Endotoxin. 



The effect of diluting an extract before mixing it with the serum allowed a 

 return to the same degree of phagocytosis as occurred in the serum saline 

 mixture, i.e., the control. Several notable exceptions were recorded, in which 

 the diluted toxic substance appeared to play the part of a " stimulin." In 

 such instances the degree of phagocytosis was far greater than in the control 

 experiments. The stimulating action of the diluted toxin appeared to be 

 specific. Tills may be briefly instanced by the following examples : — 



* Prof. Hewlett very kindly suggested to u.s that we should a.scertain whether .similar 

 results could be obtained by substituting wa.^kcd bacteria for the preparation of the 

 endotoxin, ho as to eliininato the possibility that our results might be dcpeiulont upon an 

 extracellular substance adhering to the unwashed organisms, f^xperinients were per- 

 formed for this purpose and it would seem that washed bacteria can bo enii)loyed for the 

 preparation of the bacterial extract, although the results are not quite so striking as in 

 the case of tlic unwashed. This fact could be explained possibly by the loss of bacteria 

 in the washing, and, therefore, the sniall quantity of organisms left for grinding up. 



