268 president's address — section l. 



It is remarkable that leucocytes appear more resistant to the 

 inhibitory effects of drugs than many other cells. Thus Besredka 

 has shown that they ingest particli3S of arsenic trisulphide injected 

 into the peritoneum and so protect the body. Bordet has shown 

 that morphine (1-100), cocaine (1-1,000) and atrophine. (1-1,000) 

 do not prevent phagocytosis of bacteria iii vitr<o. Quinine on the 

 other hand is extremely toxic for leucocytes. 



(4) their abilit}^ to digest the bacteria (or other cells) they 

 have engulphed, and the presence of a tryptic ferment 

 resulting from the death and disintegration of leuco- 

 cytes, especially jjolyniorphonuclears, which digests 

 tissue elements and dead cells. 



The effects of intracellular digestion of bacteria can be observed 

 directly by Wright's or Pfeiffer's methods: they swell up, stain 

 less easily, and become converted into granules. Another method 

 is tO' obtain an extract from the leucocytes and test its bactericidal 

 or digestive effects. Several methods have been used, notably by 

 Gengou (1915), who extracted the leucocytes with dilute hydro- 

 chloric acid and obtained a clear liquid which caused a breakdown 

 of bacterial cells in all respects similar to that seen in vivo. 

 Gengou noted that an extract of mononuclear leucocytes was in- 

 active, and this is in line with the inactivity of the lymphocytes 

 in phagocytosis of pyogenic organisms. The products of such 

 digestion of bacteria cannot easily be determined, but with the 

 digestion of tissue cells the end products are easily identified and 

 the nature of the ferment action is thus made clear. Muller and 

 Jo'chmann have suggested a, simple demonstration by placing 

 a drop of human Jeucocytic exudate on the surface of some coagu- 

 lated serum. Bordet has pointed out a rather remarkable thing, 

 that only leucocytic material from man, ape or dog is active in 

 this way, as though in other animals there is some inhibiting sub- 

 stance, or the. ferment is liberated only with difficulty. 



Now, bacteria owe their virulence in large measure to their aiiti- 

 phagocytary powers, and indeed virulence is in the main inversely 

 proportional to phagocytosis. An experiment by Tchistovitch 

 affords an example. He took a virulent pneumococcus and found 

 that in the mouse there was no phagocytosis, in the rabbit phago- 

 cytosis was feeble, whilst in the dog it was active and complete. 

 This agrees with the high susceptibility of the mouse, lessened 

 susceptibility of ihe rabbit, and insusceptibility of the dog. 



The comparative values of phagocytes and serum in guarding 

 against infection cannot be stated, for immunity is a product of 

 many forces with cells and sera acting in combinatiom, but as 

 showing the inability of serum alone in many cases we may note 

 the following experiments. Anthrax bacilli, towards which the 

 dog has a high degree of immunity, will nevertheless grow artifi- 

 cially quite well in dog's serum. The same is true of the fowl; 



