JOINT ACTION OF SEVERAL AMBOCEPTORS. 623 



to be incorrect. We may add that we too observed marked agglu- 

 tination on adding ox serum to the guinea-pig blood previously 

 treated with horse serum. Nevertheless, on testing the ox serum 

 separated by centrifuge, we found that this still possessed all its 

 power to effect haemolysis of guinea-pig blood in conjunction with 

 horse serum. 



By this we do not intend to combat the statements of Bordet 

 and Gay, that guinea-pig blood treated successively with horse 

 serum and inactive ox serum is resistant to the haemolytic action 

 of the active mixture. We too have made similar observations, 

 though we noted that haemolysis was absent only when the guinea- 

 pig blood-cells had been treated with an excess of horse serum. 

 Under these circumstances it was immaterial whether the pre- 

 vious treatment was only with horse serum or whether treatment 

 with horse serum was followed by digestion with inactive ox serum. 

 It is to be noted, however, that even when the guinea-pig blood- 

 cells were found resistant, there was no absorption of the haemolytic 

 component of the ox serum. 



In the following experiment, which illustrates the conditions 

 just described, we first determined the minimum amounts of active 

 horse serum and inactive ox serum which, combined, just sufficed 

 to produce complete haemolysis. This dose was found to be 0.25 

 cc. for each. 



Two parallel series were prepared. To 1 cc. 5% guinea-pig blood were 

 added decreasing amounts of active horse serum. The mixtures were kept 

 at 37 for one hour, and then centrifuged. 



Series A. The sediments of series A were digested with 0.25 cc. active horse 

 serum and 02.5 cc. inactive ox serum, the whole being made up to about 

 2.25 cc. with physiological salt solution. 



Series B. The sediments of series B were once more digested for one hour 

 at 37 with 0.25 cc. inactive ox serum (and salt solution). The mixtures were 

 then centrifuged and the sediments thus obtained mixed with 0.25 cc. horse 

 serum plus 0.25 cc. inactive ox serum. 



Series C. The supernatant fluids separated by centrifuge in series B were 

 mixed with guinea-pig blood and with 0.25 cc. horse serum. (Total volume 

 about 2.25 cc.) 



The result is shown in Table IV. 



The table shows that the guinea-pig blood-cells do not lose 

 their normal susceptibility when they are treated with a dose of 

 horse serum sufficient to produce complete haemolysis (0.25 cc.). 



