PART I. 



RELATING TO ANTIBODIES IN GENERAL, AND ANTI- 

 BODIES OTHER THAN THE PRECIPITINS. 



SECTION I. 



EHRLICH'S THEORY REGARDING THE FORMATION OF ANTIBODIES, 

 TOGETHER WITH A BRIEF CONSIDERATION OF TOXINS AND 

 ANTITOXINS. 



IN 1890 Behring discovered that the serum of an animal immunified 

 against diphtheria was capable, when injected into a fresh animal, of 

 conferring immunity upon the latter, which, failing the use of the 

 immune serum, died from the effects of the diphtherial toxin 'it 

 received. Soon after, Behring and Kitasato obtained similar results 

 with tetanus. Ehrlich (1891) next treated animals with increasing 

 doses of ricin and abrin (the toxic substances contained in the castor- 

 oil bean and the seeds of jequirity) and found that the toxin was 

 neutralized in vitro when added to the treated animal's serum, proof 

 of neutralization being afforded by the fact that when certain propor- 

 tions of toxin and immune serum were mixed in vitro, these mixtures 

 were innocuous when injected into animals. He proved that the 

 neutralizing action of immune serum upon each of these toxins was 

 specific, that is, the antiserum for abrin did not neutralize ricin, and 

 vice versa. Immunization against the toxins of snake venom had 

 already been practised by Sewall (1887), and subsequently Calmette 

 (1894) and Frazer (1895), but it was reserved for Ehrlich to throw 

 more light upon the nature of the acquired immunity to toxins through 

 the formation of antitoxins in the bodies of toxin-treated animals. He 

 and Madsen showed that toxin and antitoxin combined in definitely 



