ANTITOXINS AND RELATED ANTIBODIES 145 



shall be ten times the least quantity of antitetanic serum neces- 

 sary to save the life of a 350-gm. guinea-pig for ninety-six hours, 

 against the official test-dose of a standard toxin furnished by the 

 Hygienic Laboratory of the Public Health and Marine Hospital 

 Service." 1 



Another statement is that one-tenth of a unit, mixed with 

 100 M. L. D. of the standard toxin, contains " just enough free 

 poison in the mixture to kill the guinea-pig in four days after 

 subcutaneous injection." The amount of toxoid has not been 

 accurately determined in this test-toxin used; therefore, the stand- 

 ardization test must in all cases be in terms of the Hygienic Labora- 

 tory toxin, no other sample of toxin being suitable. The test-dose 

 is called the L + dose, as in the diphtheria toxin. 



Preparation of Other Toxins and Antitoxins. As has before 

 been stated, antitoxins have been prepared for a large number of 

 toxins. The two already discussed are by far of the greatest im- 

 portance commercially. In the development of theories of im- 

 munity considerable use has been made of antiricin and antiabrin. 

 An antitoxin for pollen (called pollantin) has been used to some 

 extent in hay-fever. Antitoxins against snake venom may be pur- 

 chased upon the market. They are of considerable importance 

 in certain tropical countries, particularly India, where poisonous 

 snakes abound. 



Antienzymes. A study of enzymes and their actions has shown 

 them to resemble toxins in some respects. Although an enzyme 

 does not form a part of the final product of its activity, it never- 

 theless seems evident that it first unites with the compound which 

 it transforms, and later is split off. Enzymes are believed to 

 possess two groups, resembling the toxins one a binding group, 

 or haptophore, and the other a fermenting group, or zymophore. 

 The injection of an enzyme into the animal body will usually 

 result in the production of an antienzyme, which will permanently 

 combine with the enzyme and effectually prevent its action. These 

 antienzymes are probably developed in exactly the same manner 

 as are the antitoxins, and have the same general constitution. 

 They are likewise very specific: the action of pepsin is inhibited 

 by an antipepsin, and not by an antirennet. 



1 Treasury Dept., Circular No. 61, Oct. 25, 1907. 

 10 



