624 



COLLECTED STUDIES IN IMMUNITY. 



TABLE IV. 



It also shows that an excess of horse serum gives rise to an increased 

 resistance of the blood-cells toward what is otherwise a hsemolytic 

 mixture, and this effect is produced whether or not ox serum is 

 subsequently allowed to act on the cells. Moreover, from Column 

 C, we see that in this case also the ox serum has not lost its ability 

 to produce haemolysis in conjunction with horse serum. Con- 

 cerning the cause of the resistance produced by treating guinea- 

 pig blood-cells with horse serum alone or with horse serum and 

 ox serum, we can only conjecture. It is quite possible that the 

 effect is due to an antagonism between agglutination and haemol- 

 ysis, as suggested by Bordet and Gay. It is also conceivable that 

 horse amboceptor and ox amboceptor attack the same receptors 

 of the biood-cells, and that preliminary treatment with an excess 

 of horse serurn blocks the way for the ox amboceptor. Be this as 

 it may, our experiments show that the ox serum component con- 

 cerned in this haemolysis is not bound when the guinea-pig blood- 

 cells are first digested with active horse serum. Bordet and Gay's 

 assumption, that ox serum produces this haemolysis through a 

 " colloid " constituent which acts only after amboceptor and com- 

 plement have combined with the guinea-pig blood-cell, must there- 

 fore be abandoned. On the other hand, Klein's observation, that 

 guinea-pig blood previously treated with horse serum is no longer 

 dissolved by inactive ox serum, is readily explained in accordance 

 with the ideas expressed by Browning. The horse serum comple- 

 ment, though not dominant for the horse amboceptor, is anchored 

 to the cell by means of this amboceptor, and thus is no longer 

 available for the ox amboceptor. We have tried to illustrate the 

 conditions in Figs. 1 and 2 of the accompanying plate. It may be 

 added that in this case it is impossible to produce haemolysis either 



