I. S. FALK 575 



colloids without regard to the acidity or alkalinity of the solution. Maver and I' have 

 found that the Field and Teague apparatus is not a true electrophoresis cell and that 

 the migrations of colloidal particles recorded in that apparatus are anomalous. In a 

 true cataphoresis cell, antitoxin is certainly and toxin is probably amphoteric. The 

 indications are that antitoxic action may depend upon a specific capacity to reduce 

 P.D. on toxin and thereby to flocculate the toxin and render it physiologically inert. 



The hypothesis that the reactions of immunity are dependent upon (or are closely 

 associated with) alterations of the P.D. on micro-organisms may not be more than 

 casually demonstrable at this time. But, viewed from a particular angle, it is not far 

 fetched. It assumes only that in the study of virulence (or of resistance) we must con- 

 sider not the microbe alone, but the microbe in an environment. The study of viru- 

 lence is a special case of the larger study of the organism, a special case in which the 

 universe of discourse is bounded by the confines of the host body. And, whether the 

 microbe be in vitro or in vivo, its P.D. is related to those characteristics which may be 

 measurable in terms of growth, reproduction, toxin production (toxigenicity), 

 virulence, resistance, and immunity. 



In concluding, I would say that I have marshaled a portion of the newer evidences 

 on the mechanisms of virulence not so much to prove a new case as to plead for a 

 reanalysis of an old one. I am persuaded that the older notions on virulence and its 

 mechanisms have not been fruitful; a newer one which for the moment places the 

 dynamics of electrical potential differences or charges as a focal point between "vir- 

 ulence" and "resistance" may not be more sound, but it cannot be more sterile. 



' Maver, M. E., and Falk, I. S.: /. Immunol., 14, 219. 1927. 



