THE NATURE OlF' TOXIN 125 



tation are phases of the same reaction, and J. Alexander ^^ has 

 seen the diphtheria toxin-antitoxin union by ultramicroscopic 

 methods. 



It will be observed that no mention has been made of the 

 so-called ''lipoids." These substances play no part in the 

 phenomenon whatever. The term ''fat" has been given a 

 somewhat elastic use to include the fatty acids and their salts 

 and esters. Cholesterol is not a lipoid but an alcohol. The 

 writers are of opinion that the evidence for the existence of hard 

 and fast lipoid substances such as lecithin and kindred bodies, 

 as such, in the fluids and cells of the body is very unsatisfactory 

 and doubtful. The mere fact that they may be extracted from 

 dried tissues by certain solvents does not signify at all that they 

 existed as entities therein. There are as many kinds of lecithin 

 as there are kinds of tissue, and, on the other hand, Barbieri and 

 his pupils^^ failed to find a trace of lecithin in 3000 eggs. The 

 availability of, if not the necessity for, dehcate, easily shifted, 

 labile adsorption compounds of electrolyte-fat-protein Vv'ithin 

 the body fluids is, however, undisputed, and it is probable that 

 the whole mechanism of immunity occurs in just such emulsion 

 colloids. The proper emulsification of bacterial and their 

 artificial antigens with emulsifying agents is regarded as the 

 sine- qua non of toxin production. The r61e of cellular protein 

 aside from some such action does not appear to be paramount 

 and is not otherwise essential to antibody formation. The 

 "type" antibody response to protein and the "specific" anti- 

 body response to cells are but phases of the same process. Fat- 

 free protein, havmg no fat at its surface, has nevertheless chem- 

 ical configuration and particulate size, factors assurmg adsorp- 

 tions and antibody production, and the antibodies respond 

 clearly to the antigen "type" only, lacking the sharp specificity 

 of cellular antibody for the very reason of the fat-free character 

 of the antigen. 



The similar behavior of true and artificial lysins and toxins in 

 relation to heat, pH, reagents, adsorbents, effects on animals, etc... 



1^ Bechhold-Bullawa, footnote, p. 195. 

 '« Gazzetta, 1917, 47, 1. 



