TOXINS AND ANTITOXINS 253 



doses he finds zones of action and of inaction occur. Thus Coventry 

 (1930) states that when she injected rats infected with T. lewisi 

 with varying doses of trypanocidal immune serum (expressed in 

 c.c. per 100 gram body weight) slie found that 1.1 c.c. had no 

 effect, 1.5 c.c. was markedly trypanocidal, 1.9 c.c. had no effect, 

 2.3 c.c. only slightly trypanocidal, while 2.7 c.c. was markedly 

 trypanocidal. 



Other Examples of the Zone Phenomenon. — Other examples 

 of what is commonly called the zone phenomenon are frequently 

 observed in antigen-antibody reactions. Larsen and Nigg (1928) 

 observed that in the Wassermann test for syphilis in individuals 

 liaving both sypliilis and leprosy they frequently observed more 

 complement fixation in the tubes containing smaller amounts of 

 patient's serum tlian in the one containing the maximum amount. 

 When one works with bactericidal sera one notes quite fre- 

 quently that there are fewer bacteria destroyed in the stronger 

 concentrations of immune serum than in high dilutions. Corre- 

 sponding exami)les of the zone phenomenon can also be dem- 

 onstrated for precipitins and agglutinins. The zone phenomenon 

 is quite characteristic of colloidal reactions. 



Danysz Effect. — ^Another phenomenon Avhich is apparently a 

 colloidal reaction is called the "Danysz effect." Danysz noted 

 that when lie added an excess of toxin to its antitoxin the amount 

 of uncombined toxin varied according to the way he added the 

 toxin to the antitoxin. If he added it in fractional amounts wdth 

 proper time intervals, there was more unneutralized toxin than 

 if the toxin were added to the antitoxin in one operation. A 

 similar phenomenon has been described for other antigen-antibody 

 mixtures. Bordet considers this an adsorption phenomenon and 

 compares it to the adsorption of dye by filter paper. If one tears 

 a piece of blotting paper into very small pieces and adds them 

 one at a time to a solution of dye, they will take up more dye 

 than if the blotting paper is added as one piece (see Wells, 1929, 

 and also Bordet, 1909). 



Thus it wdll be seen that there is considerable evidence indicat- 

 ing that colloidal phenomena play an important part in antigen- 

 antibody reactions, l^'or a more extensive discussion of the physi- 

 cal chemistry of toxins and antitoxins the student is referred to 

 a short report by Maver (1928). 



