2 7(i 



LOCAL TISSUE REACTIVITY 



guinea pig scrum. It was shown, therelore, that the cross reactions 

 ^vith heterologous sera Avere coincidental w ith cross precipitations 

 (Shwart/nian, i() ;2r/) . Hektoen and Cole (h),'^2) offered an e\- 



FiG. 33. Histoloo;ic appearance of reaction at prepared skin site four hours after in- 

 travenous injection of horse serum. High power view. Note early venous thrombosis. 



planation for cross precipitation obtained after employment of 

 large doses of antigen. 



Thtis far no refractoriness to the reacting potency of antigen -)- 

 antibody complexes was observed. The reactions ^vere repeatedly 

 obtained by the above method in the same rabbits for as many 

 as 10 times at weekly intervals. It w^s only necessary to employ 

 different bacterial filtrates for skin preparation each time to avoid 

 acc}iiirement of acti\e immiuiity. 



FORMATION OF REACTING FACTORS IN RABBITS PASSIVELY SENSITIZED 

 TO ANIMAL PROTEINS 



The assumption that the reaction at a prepared site is due to 

 in vivo interaction of the antigen injected intravenously ^vith the 



