270 



Society Proceedings (122). 



themselves to be good precipitin formers would form antibody in 

 excess earlier than upon first immunization and would therefore 

 dispose of injected antigen earlier than upon first immunization 

 and earlier than fresh rabbits injected with the same amounts of 

 antigen. 



A control series of 11 normal rabbits was injected with the 

 amounts of horse serum used in the previously immunized rabbits ; 

 precipitin and precipitinogen determinations were made similarly 

 on the controls every second or third day. Of the rabbits re- 

 ceiving 3.00 c.c. of horse serum the time of disappearance in those 

 previously immunized varied from 6 to 17 days with an average 

 of 1 1.2 days and in the unimmunized controls the variation was 

 14 to 17 days with an average of 15.5 days. In the rabbits re- 

 ceiving 6.00 c.c. of horse serum the figures were: Immunized, 

 variation 1 to 37 days, average 13.7 days. Unimmunized, varia- 

 tion 6 to 21 days; average 16.3 days. The difference, while in 

 favor of the immunized animals, certainly falls short of theoretical 

 expectations. 



Following these preliminary and somewhat inconclusive ob- 

 servations an attempt was made to determine the role of intra- 

 vascular union of antigen and antibody by a different experimental 

 procedure. Normal rabbits were injected intravenously with 

 6.00 c.c. of horse serum and then twice every day given large 

 amounts of high titer anti-horse rabbit serum intravenously. 

 Precipitin and precipitinogen determinations were made daily 

 during the period of the experiment. No conclusive evidence of 

 accelerated disappearance of antigen was observed. One rabbit 

 which received 97 c.c. of potent (1 : 20,000 to 1 : 500,000) anti-serum 

 during the 48 hours following the injection of 6.00 c.c. of horse 

 serum had the foreign serum in the circulation for 7 days. 

 Another rabbit receiving 126 c.c. of potent (1 : 20,000 to 1 : 500,000) 

 anti-serum during the 55 hours following the injection of 

 6.00 c.c. of horse serum continued to have the foreign serum 

 in the circulation for 9 days after the antigen injection. 

 While the rate of disappearance of antigen in these two rabbits 

 is below the average for normal rabbits injected only with horse 

 serum the rate is within the limits of variation of the control 

 rabbits. If such a flooding of the circulation with specific anti- 



