JOINT ACTION OF SEVERAL AMBOCEPTORS. 619 



ceptor theory. Browning also showed that a similar effect could 

 be produced with other species of blood which by themselves were 

 unable to rob horse serum of its complement. It was merely neces- 

 sary to introduce a specific amboceptor. Ox-blood, for example, 

 has no influence on horse serum. Nevertheless, when treated with 

 a specific amboceptor derived from a rabbit, it binds the horse 

 serum complement fitting inactive ox serum, and this binding 

 occurs without the prepared cells being dissolved by the horse serum. 

 According to Browning, therefore, haemolysis of guinea-pig blood 

 brought about by the combined action of inactive ox serum and 

 active horse serum is to be explained as follows: The affinity pos- 

 sessed by the ox amboceptor for horse complement is greater than 

 that possessed by the free horse amboceptor. Haemolysis occurs 

 if the ox serum and horse serum are added at the same time. If, 

 however, the horse serum is first digested with- guinea-pig blood, 

 the horse amboceptor will unite with the blood-cell. This union 

 leads to an increase in the affinity of the complementophile group 

 and causes the complement to be anchored to the horse amboceptor. 

 The union between complement and amboceptor becomes more 

 and more firm, so that after a time not even the ox amboceptor, 

 which really possesses a higher affinity than the horse amboceptor, 

 is able to disrupt the combination. (See figures 1 and 2 of the 

 accompanying plate.) 



It is apparent that Bordet and Gay were unacquainted with 

 the work of Browning. The experiments they report are largely 

 identical with those made by Klein and Browning. The follow- 

 ing interesting experiment, however, is entirely new: Ox blood-cells 

 loaded with amboceptor do not dissolve in horse serum, but do dis- 

 solve in a mixture of active horse serum plus inactive ox serum. 

 In this case, the authors rightly reason, the ox serum cannot pos- 

 sibly act as an amboceptor, but must represent a constituent neces- 

 sary for haemolysis, but identical neither with the amboceptor 

 nor with the complement. Analogously, in the combination guinea- 

 pig blood plus inactive ox serum plus horse serum, the horse serum 

 is believed to act, not as an amboceptor, but as a third component 

 effecting haemolysis. Bordet and Gay thus assume that ambo- 

 ceptor and complement are present in horse serum but are unable 

 to effect haemolysis without the presence of the third component 

 present in ox serum. This hypothetical substance they term 

 "colloide de bceuf." According to Bordet and Gay, this colloid 



