40 TOXINS AND ANTITOXINS. 



why it has been possible to produce antitoxins from 

 toxins which have lost some of their toxic proper- 

 ties, but which have preserved their property of 

 uniting with antitoxic substances. Ehrlich gives 

 the name toxoids to those modified toxins that 

 have lost their toxophore groups, while the hapto- 

 phore group, the producer of the immtmizing sub- 

 stance, is still preserved intact. 



According to Metchnikoff's theory, which is 

 very similar, it seems quite possible that the 

 phagocytes, thanks to the facility with which they 

 absorb poisons, occupy an important place as 

 producers of antitoxins. It has not been possible 

 so far to verify this theory in our at present im- 

 perfect knowledge regarding this subject. The 

 domain of immunity has, however, made brilliant 

 conquests during these last few years, so that we 

 should not despair of arriving at a definite solution 

 before long. 



In the vaccinated animal the antitoxin is re- 

 produced, and it is possible to obtain several 

 times, from the vaccinated animals, successive 

 portions of antitoxic serum.* The protective power 

 of these antitoxins is absolutely marvelous. An 

 animal accustomed gradually to the tetanic virus 

 yields a serum containing an antitoxin a thousand 

 times more active than the virus. 



* Ch. Salmonsen etTH. Madsen; Reproduction de la sub- 

 stance antitoxique. Ann. Inst. Pasteur, xii, p. 762. Roux et 

 Vaillard: Ibid., 1893, p. 83. 



