THE LEUCOCYTES IN IMMUNITY. 735 



momentary exposure to the action of the oxidizing substance. 

 A sudden arrest of the supply of the latter to the blood, as 

 occurs when a large dose of venom causes the functions of the 

 adrenal system to cease, for example, accounts for the liquid 

 blood witnessed under such circumstances. The tissues, con- 

 tinuing the consumption of oxygen, soon deplete the blood of 

 this gas, leaving none to carry on the partial oxidation of the 

 fibrinogen to which the formaiion of fibrin is due. We have 

 evidence here, therefore, through the fact alluded to by Metch- 

 nikoff, that coagulation occurs in the extravasated blood, of 

 the presence in it of at least a small quantity of oxidizing sub- 

 stance. As we view the composition of this extravasated blood, 

 therefore, it embodies (1) fibrinogen, (2) the oxidizing sub- 

 stance, and (3) the cytase, including its trypsin, as factors of 

 the process through which bacteria and blood-cells are disin- 

 tegrated. 



An application of the principles we have submitted will 

 serve to illustrate our meaning. Keferring to the labors of 

 Bordet, Metchnikoff 70 states that "whenever the serum of a 

 prepared animal is deprived of its haemolytic properties by heat- 

 ing to 55 or 56 C., this property can be restored to it with 

 certainty by adding to it a little normal serum incapable itself 

 of causing haemolysis. The heated serum of prepared animals 

 completely loses its power of dissolving its red corpuscles, but 

 it preserves its other acquired property of agglutinating the 

 latter. The red corpuscles in voluminous masses visible with 

 the naked eye remain intact indefinitely if allowed to remain 

 in the prepared and heated serum. But if a small proportion 

 of normal blood (obtained from many species of vertebrates) is 

 added, dissolution of the corpuscles soon follows. There is 

 initiated under these conditions a process in which two sub- 

 stances take part, one of which was present in the heated serum 

 of the prepared animal, and the other in the non-heated normal 

 serum. The first of these substances which resists not only the 

 temperature of 55 to 56 C., but stands, without undergoing 

 alteration, heating up to 60 to 65 C. corresponds with the 

 intermediary substance of M. Ehrlich [our oxidizing substance] . 



Metchnikoff: Loc. cit., p. 97. 



