PHAGOCYTOSIS 35 



protective action exerted by the living leucocytes 

 against bacterial infection, and the relation of these 

 cells to the blood serum ; furthermore, that while our 

 knowledge of the blood serum, as developed at present, 

 shows that phagocytes may be aided by this in the 

 ingestion of bacteria, the subsequent digestion of the 

 germs, and possibly the neutralisation of their intra- 

 cellular poisons, is, as far as we know, largely 

 accomplished by the unaided phagocytic cell. The 

 thought is obvious, therefore, that in the struggle 

 with bacterial invasion the leucocytic defenders might 

 be greatly reinforced if they were furnished as 

 directly as possible with a further supply of the very 

 weapons they were using in the fight with the micro- 

 organisms. Hiss has produced an extract of the 

 chief cells usually found in exudates, as he assumes 

 that extracts would be more potent than the living 

 leucocytes themselves, since, if diffusible, they would 

 be impartially distributed to all parts of the body by 

 the circulation. They would then, as quickly as 

 absorption would permit, relieve the fatigued leuco- 

 cyte, and also protect, by any toxin-neutralising or any 

 other power they might possess, the cells of highly 

 specialised functions. Hiss claims to have very good 

 results in the treatment of staphylococci and strepto- 

 cocci infections by the use of this leucocytic extract. 



Several other authors have shown that these leuco- 

 cytic extracts contain bactericidal substances which 

 are called " endolysins." These substances in 

 structure are quite different from that of serum 



