INTERREACTIONS OF TOXIN AND ANTITOXIN QI 



destroyed ; the destruction occurred, however, sooner at the 

 cathode than at the anode, suggesting that it was a negative 

 colloid. They found it to be precipitated by positive colloids, 

 such as colloidal hydrated oxide of iron or chromium, though this 

 action occurred only in vitro, not in vivo. Tetanus antitoxin, how- 

 ever, did not lose its activity when exposed to mineral colloids. 



Further, there is an approach to the phenomenon of specificity 

 in the adsorption of one colloid by another, since certain colloids 

 are only precipitated by certain other colloids ; the specificity, 

 however, is by no means so exact as in the case of the toxins, etc., 

 and their antibodies. 



A further analogy arises in the explanation of the difference 

 between the L and L + dose, which is paralleled by the relation- 

 ship between colloidal ferric hydroxide and arsenious acid. When 

 these two substances are mixed adsorption and precipitation take 

 place ; hence the use of the former substance as an antidote for 

 the latter. Now it is found that if a solution of arsenious acid is 

 just rendered toxic by the addition of ferric hydroxide, very much 

 more than one lethal dose of arsenic must be added to make the 

 mixture toxic again. 



The further investigation into the evidence which they have 

 adduced would lead us too far into the study of the agglutinins to 

 be undertaken here. It will be dealt with subsequently (see 

 Chapter XII.). 



It seems, on the whole, that no theory is absolutely sufficient to 

 explain all the phenomena, and that as soon after each new one is 

 adduced the supporters of the older ones bring forward evidence 

 which renders it untenable. The probability is, at the time of 

 writing, that Ehrlich's views are generally held, and are open to 

 the fewest objections. They are complicated, it is true, and have 

 had to undergo constant modifications as new facts have arisen ; 

 but the facts themselves are complicated. Yet it must be con- 

 fessed that there are some grave objections to its acceptance in its 

 present form, and it may become yet more involved before it can 

 be fully accepted as a complete explanation. Thus the analogy 

 with other bodies, and the phenomena of the death from intoxica- 

 tion of animals with antitoxin in their blood, seem to point strongly 

 to the theory that the toxin-antitoxin molecule dissociates strongly 

 both in vivo and in vitro. Yet this is not compatible with Ehrlich's 

 views. 



