THE LEUCOCYTES IN IMMUNITY. 743 



views as to the action of alexins. It is now plain that general 

 destruction of cellular elements would prevail were the physio- 

 logical co-ordination of all functions, including those of the 

 blood, not as perfect as it is. Buchner's interpretation of the 

 destructive action of alexins and of bacterial products is never- 

 theless justified; but it lacks the all-important controlling 

 factors we have described to -restrain this action within proper 

 limits. Indeed, our organism produces trypsin to destroy bac- 

 teria which also produce kindred toxins capable of destroying 

 us. It is primarily upon the integrity of our adrenal system 

 and of the protective agencies that it governs, therefore, that 

 our safety depends when bacteria, their toxins, vegetable poi- 

 sons, and venoms penetrate the blood-stream, notwithstanding 

 the barriers with which the intestinal and respiratory tracts are 

 supplied to oppose their entrance therein. 



But do the trypsin and the oxidizing substance simulta- 

 neously accumulate in the blood-stream? Trypsin being, as 

 previously stated, the agglutinating body and the fixative the 

 oxidizing substance, the following additional quotation from 

 MetchnikofFs work 80 will show that such is the case: "The pres- 

 ence of the fixative, this other important element in immunity, 

 could only be demonstrated in normal humors in exceptional 

 cases and in small quantities. The agglutinating properties of 

 these humors also showed themselves as but slightly developed, 

 and devoid of importance in natural immunity. In acquired 

 immunity against microbes we see, on the contrary, the bac- 

 tericidal and agglutinative powers of the humors increased to a 

 great proportion." 8 * As viewed from our standpoint, however, 

 the bactericidal and agglutinative properties are both inherent 

 in the trypsin; the oxidizing substance plays as elsewhere in 

 the organism its role as a reagent, with the fibrinogen as the 

 primary source of energy. This energy, manifested as heat, 

 endows the trypsin not only with the power to convert toxins 

 and diastases secreted by bacteria, toxalbumins, including vege- 

 table poisons and venoms, into harmless products, as stated in 

 the previous chapter, but it also enables it to destroy bacteria. 



*> Metchnikoff: Loc. cit., p. 264. 

 81 All italics are our own. 



