MARY E. MAVER 741 



signify that antitoxin is a definite protein with properties sHghtly different from the 

 corresponding protein in normal serum. Wells' has discussed at length the view that 

 the highly specific character of toxin-antitoxin reactions can be most readily ac- 

 counted for when to these reagents are assigned the complex structures of proteins. 



After the colloidal nature of toxins and antitoxins had been established, Biltz, 

 Much, and Siebert^ applied to immune sera and toxic broths the electro-colloidal re- 

 actions of inorganic and organic colloids. They found that tetanus toxin and anti- 

 toxin were precipitated by positive colloids but were unable to demonstrate the 

 cataphoretic migration to the anode. Zunz^ found that animal charcoal adsorbs 

 diphtheria and tetanus toxins and antitoxins, but not the mixture of toxin and anti- 

 toxin. He was unable to detect any relation between the adsorption of toxins and 

 antitoxins and modifications of the solution containing them in regard to density, 

 index of refraction, or freezing-point. Toxins lowered the surface tension of the 

 solutions but antitoxins did not alter it. Adsorption studies of the pseudoglobulin 

 fraction from immune sera have yielded interesting results. Reitstotter^ has shown 

 that a complex ferric hydroxide-pseudoglobulin sol prepared with immune pseudo- 

 globulin was more sensitive to flocculation by electrolytes than a corresponding sol 

 made with ferric hydroxide and normal pseudoglobulin. Since it is probr.ble that 

 the particles of the sol are kept from flocculating by their similar charges, this would 

 indicate that the immune pseudoglobulin had caused a greater decrease of the charge 

 on the complex sol than the normal pseudoglobulin. 



The neutralization of diphtheria toxin by antitoxin and of ricin by anti-ricin has 

 been studied by Biltz^ as adsorption reactions, and his calculations indicate that these 

 reactions obey Gibbs's adsorption formula. The extent to which the electro-colloidal 

 theory can explain the specificity of immunological reactions depends upon our inter- 

 pretation of the source of the charge carried by the adsorbing particles. If the charge 

 exists by virtue of the ionization of a characteristically oriented surface molecule*" 

 the specificity of the reaction can be explained ultimately upon a chemical basis. In 

 defense of the idea that these specific biological reactions can be adsorption reactions, 

 Freundlich says: 



This [specificity] is by no means in contradiction with the view of an adsorption, no 



matter whether it be regarded as a saturation of the last residual valencies, or whether it be 



brought into relation with the lowering of interfacial tension; for even in the last case the 



da . 

 differential coefficient ~r- in the Gibbs' formula might depend specifically upon the nature of 



adsorbent and adsorbed substance. But it is certainly a gap in the theory of these phe- 

 nomena that up to the present this specific adsorption has been shown only by substances 

 formed in biological processes and not by those prepared in the test tube. The idea suggests 

 itself that only an adsorbent of suitable geometrical form is able strongly to adsorb a sub- 



' Wells, H. G. : Chemical Aspects of Immunity. 1925. ^ Loc. cit. 



^Zunz, E.: Bull. Acad. roy. ined. de Belg. Oct. 29, 1911. 



4 Reitstotter, J.: Ztschr.f. Imiminitdlsforsch. u. expcr. Therap., 30, 507. 1920. 



5 Biltz, W.: Biochem-. Ztschr., 23, 37. 1909. 



'Harkins, W. D., and Beeman, N.: Proc. Nat. Acad. Sc, 11, 631. 1925; Langmuir, I.: Colloid 

 Symposium Monograph, 4, 48. 1925. See also chap. Iviii, this volume, by Northrop. 



