MECHANISM OF ANTIBODY FORMATION 141 



three weeks later when antibody protein containing 0.05 mg. N was 

 injected intravenously. Similarly sensitized guinea pigs failed to react 

 to normal horse plasma diluted to 1:10, but four out of six reacted to 

 normal undiluted plasma containing 0.5 mg. of protein nitrogen, 

 which probably, as stated by Northrop, indicates the presence of 

 minute amounts of normal protein in the purified antibody preparation. 



