596 COLLECTED STUDIES IN IMMUNITY. 



blood-cells, so that finally all the blood-cells in the' mixture contain 

 an amount of amboceptor, sufficient, when suitable amounts of 

 complement are added, to produce complete solution of the entire 

 mixture. This is shown by the following experiments. 



To 20 cc. 5% serum-free suspension of ox blood-cells one adds 

 4.0 cc. inactive serum of a rabbit immunized against ox blood. 

 The complete solvent dose of this immune serum (for 1 cc. 5% sus- 

 pension) when 0.1 cc. guinea-pig serum is added as complement, 

 is 0.0015 cc. The amount employed in this experiment therefore 

 contained 130 amboceptor units. The mixtures were kept at 38 

 for one hour, and frequently shaken. The blood-cells were sepa- 

 rated by centrifuge, and washed three times with 40 cc. salt solution, 

 and then made up to the volume of the original suspension. The 

 last wash water was free from amboceptor. One cc. of this sus- 

 pension was mixed with one cc. of a fresh 5% suspension of ox 

 blood-cells, and the mixtures kept for one hour in a water-bath 

 at 40. On adding 0.2 cc. guinea-pig serum, it was found at the 

 end of fifteen minutes that complete solution of the entire quantity 

 of blood had ensued. 



This shows that in the course of one hour at 40, the blood-cells 

 added afterwards had absorbed at least sufficient amboceptor to 

 effect solution. Similar experiments with blood-cells laden with 

 3, 6, 10, and 60 times the amboceptor unit yielded entirely analogous 

 results. The action takes place even at C., though much more 

 slowly. 



The result of these experiments is apparently at variance with 

 earlier statements, that the fluid is free from amboceptors. It is 

 obvious that the amboceptors can only get from one blood-cell 

 to another by way of the fluid medium. The contradiction, how- 

 ever, is explained by assuming that the fluid is not absolutely free 

 from amboceptors, but contains such minute traces that they 

 escape detection. When, in the experiment, the blood-cells subse- 

 quently added combine with the amboceptors present in the fluid, 

 conditions are produced whereby, in accordance with the law of 

 chemical equilibrium, additional small traces of amboceptor are 

 liberated into the fluid. With the anchoring of this by the fresh 

 blood-cells, the process is repeated, so that the latter bind more 

 and more amboceptor. 



In the binding of the amboceptors we are therefore dealing 

 with a reversible process in which the equilibrium is such that 



