THE LEUCOCYTES IN IMMUNITY. 731 



substances: (1) Buchner's alexin, a product of leucocytes; (2) 

 a body which, though present in small quantities in the plasma 

 during health, i.e., under normal conditions, was found to 

 greatly increase in quantity in infected animals. Referring to 

 these investigations, and to those of Pfeiffer, reviewed in our 

 eleventh chapter, Metchnikoff 66 writes: "The researches of M. 

 Bordet 67 have definitely elucidated this question. This scien- 

 tist has demonstrated that* Pf eiffer's phenomenon is produced 

 by all sera with the aid of the same substances, which are the 

 cytases (alexin, or Ehrlich's "complement). But in the serum 

 of vaccinated animals there is added to them the fixative (the 

 substance sensibilisatrice of Bordet or immunizing body, Ehr- 

 lich's amboceptor), which itself shows specific properties. After 

 having well distinguished one from the other, the two sub- 

 stances that intervene in the granular transformation of vibrios, 

 M. Bordet has proven that in vaccinated animals it is the 

 fixative which increases in quantity, while the cytase (alexin) 

 remains as to quantity in about the same proportion as that 

 observed in normal animals." . . . "While the cytase does 

 not increase as the result of vaccinal injections, the fixative, on 

 the contrary, becomes more and more abundant. It is this 

 second soluble ferment which imposes its characteristic upon 

 the blood-stream." 



If this fixative, amboceptor, intermediary body, etc., is the 

 oxidizing substance, are we justified in granting it a position 

 in immunity overtopping that of all other agencies? In other 

 words, does Buchner's alexin, Ehrlich's complement, Metch- 

 nikoff's cytase, etc., play as insignificant a role as the experi- 

 ments referred to suggest? 



We have furnished evidence to the effect that the bac- 

 tericidal phagocytes, the neutrophiles, absorbed trypsin (the 

 spleno-pancreatic secretion) not only in the intestinal canal, 

 but likewise in the portal vein. To this secretion we ascribed 

 the destruction of all toxic albuminoids, toxins, vegetable poi- 

 sons, venoms, etc. Bacteria being likewise ingested, they nat- 

 urally find their doom in the digestive vacuoles of the pha- 

 gocytic neutrophiles, through the effects upon them of the 



66 Metchnikoff: L'lmmunitS dans les Maladies Infectieuses," p. 204, 1901. 



67 M. Bordet: Annales de 1'Institut Pasteur, vol. ix, p. 462, 1895. 



