214 Dr. A. E. Wright and Stafi-Surgeon S. T. Keid. [Oct. 21, 



incitor element in the immune serum exerts an opsonic action upon the 

 bacteria, preparing them for phagocytosis. 



Sources of Fallacy which must he Eliminated he/ore the Question as to the 

 Nature of the Incitor Element in tJte Heated Serum can he Properly 

 Investigated. 



Before an inquiry into the nature of the incitor constituent of heated 

 " immune serum " can be properly taken in hand, the sources of fallacy 

 which are incident to such an inquiry must be realised. A first source of 

 fallacy is associated with the occurrence of spontaneous phagocytosis. A 

 second source of fallacy arises, as we shall see in a subsequent section, in 

 connection with the fact that the incitor power of the heated immune 

 serum is influenced in a remarkable and, for the present, quite inexplicable 

 manner by the duration of the exposure to heat and by the temperature 

 employed. 



Fallacy of Spontaneous Phagocytosis. 



It will enforce itself upon the mind on considering the protocols of 

 the original experiments published by one of us in conjunction with 

 Douglas in these 'Proceedings'* that the phagocytosis is not completely 



bacteriotropic substances (' Lancet,' December 23, 1899) as against Neufeld the right of 

 assigning to this term its technical signification. 



Dean likewise, while championing the view that the incitor elemeut is an opsonin, and 

 while dissatisfied with the ambiguity of the terms "fixateur" and "substance sensibili- 

 trice," and while conceding that " it may be convenient to adopt the term opsonin," 

 employs instead the periphrasis " tlve substance which prepares the micro-organisms for 

 phagocytosis" denying himself the convenience of the term opsonins " in order to mark 

 the danger that one might be led to regard the opsonin as actually a different substance, 

 and not merely a property of immune serum." My fellow- worker, Douglas, and I have not 

 claimed for ourselves anything more than this : that we have, by the aid of an accurate 

 quantitative method, adapted from Leishman, placed in a clear light the rdle of the blood 

 fluids in relation to phagocytosis, a role which was practically everywhere ignored or 

 misconceived, and which had at best been "glimpsed" by one or two observers whose 

 work, undertaken with very defective and fallacious technical methods, was, as Dean's 

 own analysis shows, of a very unconvincing character. "We submit that the clarification of 

 the role of the blood fluids which was effected by us would have remained incomplete and 

 ineffective if we had not alighted on the terms " opsonic power " and " opsonins," or some 

 other apposite and equally convenient nomenclature to denote, as the case may be, the 

 power or 11 the substance in the serum which prepares the micro-organisms for phagocytosis." 



"We would also submit that the ultimate — and we hold for the present unapproachable 

 question — as to whether the opsonic effect we have described is only one of a series of 

 diverse effects exerted by a single antitropic substance, or whether it is the result of the 

 specific activity of an independent chemical unit in the serum, is not prejudged by the 

 employment of the term opsonin. 



* Vols. 72, 73, and 74. 



