262 STUDIES IN IMMUNITY. 



ing of equilibrium between the dose of active substance absorbed 

 and that which remains free, and so forth), and this idea we have 

 endeavored to prove experimentally. 



We may add that this interpretation has appealed to various 

 observers who have performed similar experiments ; similar and even 

 more demonstrative results have been obtained, as certain of these 

 other experiments are less open to criticism than our own. The 

 researches of Eisenberg and Volk,* giving definite information on 

 the relations between agglutinins and bacteria and leading to many 

 new and important experiments on this subject, are particularly 

 instructive in this connection. These authors found that the law 

 of definite proportions does not apply to the union of the agglu- 

 tinin with 'the agglutinable substance of bacteria. In the course 

 of their work they noted that if a dose A of bacteria is added to 

 a given dose of agglutinating serum the results are the same as 

 those just described for hemolytic serum, and depend on whether 

 A is added all at once or in divided doses : less bacteria are agglu- 

 tinated when added little by little. Bacteria can absorb much 

 more agglutinin than is necessary to clump them. If the amount 

 of agglutinin is considerable, an equilibrium is established between 

 the fraction that remains free and the one absorbed by the bac- 

 teria, the degree of saturation depending on the concentration of 

 the agglutinin. We cannot reproduce here in detail the interest- 

 ing conclusions of these observers (variations in the coefficient of 

 absorption in proportion to the dose of agglutinin, the function 

 of the relative concentrations of [agglutinin and agglutinable sub- 

 stances, etc.); the most important fact is that the agglutinable 

 substance absorbs amounts of agglutinin that vary according to the 

 relative proportions of the two reacting substances. 



It would seem legitimate, then, to assume that the law of fixed 

 proportions is not applicable to the absorption phenomena by 

 cells or bacteria for the active principles of specific sera. The pro- 

 portions would seem to vary as markedly as do the conditions of 

 experiment. The conditions are very unlike those met with in 

 straight chemistry, which depend on equations and equivalents. 

 It is simply for the purpose of expressing this idea more emphatically 

 that we have compared these phenomena with those of dyeing. 

 * Zeit. fur Hygiene, Vol. XL, 1902. 



