NEUTRALISATION OF H^EMOLYSINS 193 



Evidently the effect depends upon some slow molecular 

 change in the antitoxin which is not bound by toxin. This 

 process goes on only in the presence of the neutralisation 

 products of toxin and antitoxin or of free toxin itself, 

 which therefore may be assumed to bind the transformed 

 antitoxin, so that the reaction can proceed further. The 

 circumstance that the effect of Danysz is not observed 

 with cobra poison seems to indicate that it is the poison 

 itself which binds the transformed antitoxin. For in this 

 special case the neutralisation is nearly complete, just as 

 the neutralisation of a strong acid with a strong base ; and 

 therefore, if the antitoxin is present in excess, no sensible 

 quantity of free poison exists in the solution, and hence 

 we should expect that the effect would not be apparent. 



Because of the inverse reaction of the reaction-products, 

 new quantities of toxin are always free to bind the trans- 

 formed antitoxin. This new reaction of (the modified) anti- 

 toxin and toxin is much nearer a complete one than the 

 chief reaction between these substances which prevails 

 during the first time of reaction, and which therefore 

 corresponds to the equilibrium studied before. Conse- 

 quently we find that the bond between toxin and antitoxin 

 "is strengthened with time." Therefore also the toxicity 

 of solutions containing an excess of antitoxin is found to be 

 inferior to the calculated value. In this way it is explica- 

 ble that mixtures with a very large excess of antitoxin may 

 be practically harmless, although the calculation does not 

 indicate it. This circumstance explains some experiments 

 of Madsen, in which he allowed an "innocuous" mixture 

 of diphtheria-toxin with antitoxin (hence containing a very 

 great excess of free antitoxin) to diffuse into a gelatinous 



