176 LIFE OF ELIE METCHNIKOFF 



sensitive than cytasis to high temperatures and can 

 bear a temperature of 65 to 68 C. It is incapable, 

 by itself, of killing and digesting, but by fixing on 

 them, it bites them, so to speak, and makes them 

 sensitive to the action of the phagocytic cytases, 

 which can thus digest them more easily. 



The fixator may be compared to enterokinase, a 

 special ferment in the small intestine of higher animals 

 which also does not by itself digest food but which 

 activates in a high degree the digestive power of 

 pancreatic ferments. However, it has the property 

 of fixing itself on fibrin ; it is obvious that entero- 

 kinase and the fixator have the same essential 

 properties. This similarity again proves that the 

 destruction of morbid agents by the phagocytes 

 really corresponds with actual digestion. 



It is in consequence of the digestion of vaccinal 

 products that the phagocytes manufacture the fixator. 

 Created at the expense of a given vaccinal substance, 

 the fixator has a specific character which corresponds 

 with that substance, whereas the cytase already 

 existing within the phagocytes never has a specific 

 character. 



Artificial immunisation generally produces the 

 formation of so great a quantity of fixators that the 

 phagocytes are unable to retain them and excrete them 

 in part in the ambient humors, i.e. the blood plasma, 

 or serum. When, afterwards, virulent morbid agents 

 (microbes or figured elements) are introduced into 

 an organism which has been immunised against them, 

 they are at once faced, in the humors, with fixators, 

 which immediately exert a biting action on them 

 and render them sensitive to the action of the 

 intracellular cytasis of the phagocytes. The same 



