xxi] PATHOGENIC ORGANISMS 571 



further broken up and removed — phagocytosis. It is clear 

 that a compromise between the two views : {a) MetchnikofFs 

 of phagocytosis and (^)Buchner'sof alexines, is easily possible; 

 and, Kanthack's and Hardy's researches having indicated 

 such a compromise, it is satisfactory to find that Metchnikoff 

 himself has already placed himself more in harmony with the 

 ascertained fact of acquired immunity by suggesting that 

 the inimical or inhibitory power of the blood (plasma, serum, 

 and lymph) in acquired immunity is due to the presence in 

 the blood of substances secreted or elaborated by the tissue 

 cells. This is in so far a welcome admission as we can 

 easily extend it to natural immunity by saying that in 

 insusceptible tissues or an insusceptible animal the alexines, 

 like other substances, are secretions, or products, or what- 

 ever we like to call them, of the living tissue cells, and this 

 would also well harmonise with Kanthack and Hardy's de- 

 monstration of a direct process of destruction of anthrax 

 bacilli by the secretions or the products of living cells 

 (eosinophile cells). Phagocytes, i.c^ cells which actually 

 are capable of embodying bacteria living, injured, or dead 

 in the process of the destruction and removal of the 

 microbes from the insusceptible tissue or insusceptible 

 body, are in no way opposed to the theory of alexines, since 

 the alexines themselves are substances produced by, and 

 freed from, the living cell protoplasm, and it would make 

 little difference whether the inhibitory or germicidal action 

 by alexines takes place within the cell protoplasm of some 

 cells, or by the alexines originally produced by the cells 

 but now free in the tissue juices. 



Acquired or artificial immunity. — The observation that in 

 some infectious diseases one attack protects against a second 

 underlies, as stated on a previous page, the whole theory 

 and practice of protective inoculations, but only within 



