TOXIN AND ANTITOXIN 123 



identical with those which would be produced by a fully saturated 

 mixture of toxin and antitoxin, or by intact toxin. 



III. Between these two extremes, free toxin and entirely neu- 

 tralized toxin, one can imagine many transitions, progressive stages 

 of attenuation. Every time that one mixes toxin and antitoxin in 

 the same way one attains the same degree of attenuation. 



Briefly put, this means that Bordet estimates toxin-antitoxin 

 combinations of different degrees of toxicity as representing differ- 

 ent stages in the completeness of- the saturation of the individual 

 toxin units. When 10 parts of toxin are added to 1 part of anti- 

 toxin, the result, according to him, would not be such that 1 part is 

 neutralized by 1 part of antitoxin, leaving 9 parts of toxin free. He 

 assumes rather that each unit of toxin is attenuated by the absorp- 

 tion of Ath of a part of antitoxin. He compares this process to the 

 action of iodin upon starch. Starch can absorb variable quantities 

 of iodin and, according to the amount taken up, is colored slightly 

 or deeply blue. This mode of action is common to most staining 

 processes. The substance that is stained fixes varying quantities of 

 coloring matter and the coloring matter does not limit itself to a 

 definite fraction of the substance stained but distributes itself equally 

 to the material, coloring it slightly or deeply, in its entirety, accord- 

 ing to the relative amount of color added. We will see later that 

 there are many reasons for regarding other antigen-antibody com- 

 binations as following similar laws of proportion. 



Bordet and others speak of this point of view as the "Absorption 

 Theory," and Biltz, in studying this point of view by physical 

 methods, comes to the conclusion that the observed figures of the 

 quantitative relations between toxin and antitoxin in the process of 

 neutralization are fairly consistent with the values to be expected if 

 the process were actually an absorption phenomenon. 



A curious occurrence which seems to bring the toxin-antitoxin 

 reactions close to colloidal reactions in general is that which is 

 known as the "Danysz 24 Effect" or as the "Bordet 25 -Danysz Phe- 

 nomenon." Danysz discovered that when ricin or diphtheria toxin 

 were brought into contact with their homologous antibodies the de- 

 gree of neutralization depended upon the manner in which the two 

 were put together. When the toxin was added to the antitoxin in 

 two fractions, a considerable time being allowed to elapse between 

 the additions, the final mixture was much more toxic than when the 

 total amount was added at once. In other words, although both 

 mixtures contained exactly the same quantities of the two reacting 

 substances; nevertheless the amount of toxin left free varied in the 

 two cases, according to the speed with which they had been put to- 



24 Danysz. Ann. de VInst. Past., Vol. 16, 1902. 



25 Bordet. Ann. de VInst. Past., Vol. 17, 1903. 



