508 Mr. G. Dean. On the Nature of the [July 8, 
in recurrent fever, come to the conclusion that the immune substance, or 
“fixateur,” acts as an intermediary body between the micro-organism and the 
leucocyte, transforming the negative chemiotaxis of the latter into a positive 
chemiotaxis. They state that the “ fixateur ” may act in two ways :— 
(1) The leucocytes may absorb the “fixateur,” and acquire the chemical 
affinity necessary to enable phagocytosis to occur. 
(2) The “ fixateur,’ which is present in a free state in the plasma, becomes 
fixed on to the spirilla, to which it communicates the chemical 
affinity for the protoplasm of the leucocytes, and phagocytosis 
results. 
The latter hypothesis is not invalidated by the fact that no Pfeiffer’s 
phenomenon (of bacteriolysis) can be obtained by supplying alexin to the 
spirilla, since a much smaller quantity of “fixateur” may be necessary for 
phagocytosis than for bacteriolysis. 
Savtschenko (1902), in a later work, comes to similar conclusions, based 
chiefly on experiments on the phagocytosis of red blood-corpuscles. The 
immune substance, or “fixateur,’ can fix itself on the microbe, or on the 
leucocyte, and has an affinity for the cytase contained in the leucocyte. It is 
probable, he thinks, that it acts as a stimuline for the phagocyte. He holds 
that it acts as an intermediary body between the leucocyte and the microbe, 
and merits fully Ehrlich’s designation of “ Zwischenkorper” (intermediary 
body). 
Levaditi (1901) showed, by experiments in vitro, that cholera vibrios were 
ingested by the polynuclear leucocytes of the peritoneal exudate of a normal 
guinea-pig, and that the intracellular vibrios were converted into granules 
(intracellular, Pfeiffer’s phenomenon), whereas the extracellular organisms 
remained unaltered. From a series of experiments, he came to the conclusion ~ 
that this result was due to the presence of “ substance sensibilisatrice,” in 
sufficient quantity to enable phagocytosis to occur, the complement for the 
intracellular change of the vibrios into a globular form being, he believed, 
suppled from the leucocyte itself. 
On the other hand, the extracellular solution of the microbes did not take 
place owiney to a lack of complement. The leucocytic origin of the 
complement will not be approached in the present paper. 
Levaditi also showed that the vibrios on to which the “substance 
sensibilisatrice” had been fixed when introduced into the circulation of a 
normal animal were rapidly phagocyted, just as they are in the case of an 
actively immunised animal. The extraphagocytic conversion of the vibrios 
into the granular form does not take place if sufficient precautions are 
observed to avoid injury to the leucocytes. 
