IMMUNITY. 369 



have been rendered active and brought into 

 solution through the stimulus of a foreign pro- 

 teid, and which in general act germicidally or 

 antidotally. 



Now C. Frankel and Sobernheim have 

 as a matter of fact shown that by heating 

 protective serum to 70 the bactericidal and 

 antitoxic substances are destroyed, while the 

 serum continues to exert a protective effect. 

 The anomaly may be only apparent, and due 

 to overhaste in generalization. The physical 

 participation of the tissue-cells, of the wander- 

 ing-cells, and of other mechanical aids, and also 

 the share of the chemical protective substances 

 of the blood (alexins) and of other chemical in- 

 fluences may be developed in different degrees 

 in individual cases, and may manifest their 

 activity differently according to the mode of 

 attack of the parasites ; just as the parasites 

 themselves sometimes produce their effect 

 chiefly through their multiplication, sometimes 

 chiefly through formation of poison. 



In every case the human organism possesses 

 within itself powerful means of defence, both 

 cellular elements and chemical substances. 

 The latter are derived directly or indirectly 

 both from the stationary tissue-cells and the 

 motile wandering cells ; these chemical sub- 

 stances enable the organism to cope with sap- 

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