1IIIC PRECIPITIN REACTION. 



Rabbit P^i was injected \\ith goat serum. The an list-rum so 

 obtained was repeatedly titrated against standard goat antigens 

 at a P H of 7. A double series of dilutions was made so that the 

 succeeding tubes in the series had concentrations of antigen 50 

 per cent, less than their predecessors. The results of twelve 

 such titrations are shown in Table I. 



TABLE I. 



RANGE OF ERROR IN READING THE RING TEST. 

 Antigen 2 Per Cent. Goat Serum, Antiserum P4i. 



Table showing 12 titrations of the same antiserum and antigen using a double 

 series of tubes and dilutions. 



