38 COLLECTED STUDIES IN IMMUNITY. 



tive immune body is produced, which then combines secondarily 

 with the complement present in the blood, or whether the two sub- 

 stances reach the circulation together, can under favorable con- 

 ditions be answered by an exact quantitative analysis of the immune 

 serum for immune body and complement. 



I have therefore treated a number of rabbits with cattle blood, 

 cow's milk, and tracheal epithelium of cattle, and examined the 

 hsemolytic immune sera thus obtained for their exact content in im- 

 mune body and complement. Corresponding to the material injected, 

 the erythrocytes of cattle were always used as a reagent. The 

 method employed was the same in all cases ; decreasing amounts of the 

 various blood sera were mixed, each with one-half cc. 5% cattle 

 blood dilution (in 0.8% NaCl solution), the mixture was kept at 

 37 C. for two hours and tested for haemolysis. It was then very 

 readily proven that an equivalence between immune body and com- 

 plement does not at all exist. 



If such an equivalence were present, the immune body of the 

 fresh immune serum would be completely saturated with complement 

 and would not become more active by the further addition of com- 

 plement. The experiments demonstrated the contrary, for in some cases 

 the power of the immune sera was markedly incraseed by the addi- 

 tion of normal rabbit serum, which, in the doses employed, was not 

 itself able to effect the slightest solution of the cattle blood-cells. 

 For example, if the fresh serum of a rabbit which had been treated 

 with cattle blood was able to make ten times its volume of a 5% 

 cattle blood mixture completely laky, the same serum on the addi- 

 tion of a sufficient amount of complement was able to dissolve 320 

 times its volume. On comparing the various immune sera with each 

 other, it is seen that this increase in the hsemolytic action on the 

 addition of complement is in direct proportion to the amount of im- 

 mune body present. 



The experiments therefore prove that quantitatively the immune 

 body is entirely independent of the complement. 



We can, however, go further and determine quantitatively the 

 exact amount of complement contained in the normal serum on the 

 one hand and in the immune serum on the other. 



The amount of complement contained in the various normal 

 sera was determined by always testing with the same amount of a 

 blood immune body. In fixing such a standard serum it is only neces- 

 sary to take as a measure the action of an immune body saturated icith 



