346 INFECTION AND IMMUNITY. 



able that its action in the animal body would be of 

 a similar nature. The results left no doubt in the 

 mind of Ehrlich that antiricin unites chemically 

 with ricin, and the applicability of this principle 

 in animal experiments became all the more ap- 

 parent when it was shown that the proportion of 

 antiricin which protects in vitro also protects in 

 vivo. It is held that similar proof of chemical union 

 between bacterial hemolysins, the hemolysin of 

 venom and the leucocidin of the staphylococcus 

 with their respective antitoxins is equally valid. 

 chemical Na- Although the animal body can not be dispensed 

 Neutralization with in testing the action of the antitoxins of 

 f n^ diphtheria and tetanus, certain principles of chem- 



ical action are found to prevail which leave no 

 doubt in regard to the chemical neutralization of 

 the toxins. If neutralizing proportions of diph- 

 theria toxin and antitoxin be mixed in a test-tube 

 and injected immediately, the serum does not af- 

 ford absolute protection; if, however, the mixture 

 is allowed to stand for from fifteen to twenty min- 

 utes before injection, the protection is absolute. 

 This alone would point to an action of the anti- 

 toxin on the toxin, for the completion of which a 

 certain amount of time is required. For the com- 

 plete neutralization of tetanus toxin by its anti- 

 toxin about forty minutes are necessary at ordinary 

 temperatures. Then certain other chemical princi- 

 ples described in Chapter XII, are found to hold 

 true: That neutralization proceeds more rapidly 

 at higher than at lower temperatures, more rapidly 

 in concentrated than in dilute solutions, and that 

 it takes place in accordance with the law of mul- 

 tiple proportions. 



