144 INFECTION AND RESISTANCE 



the heat-sensitive substance in the normal goat serum. And further- 

 more, in attaching to this heat-stable element, the blood cells have 

 removed it from the solution. For we have seen, in the experiment, 

 that addition of corpuscles and normal serum to the supernatant fluid 

 resulted in no hemolysis, showing that the third necessary element, 

 originally in the mixture, had been carried down with the red cells. 

 In these and other experiments then, it was shown that only the 

 heat stable substances could be fixed by the red cells, and this even 

 at temperatures at or about C. (a fact which indicates the strong 

 affinity between the two substances), while the heat-sensitive 

 "alexin," which Ehrlich now called "complement ," could not attach 

 directly to the red cells. For if such complement, in the form of 

 fresh serum, was added to washed red blood cells, and the mixture 

 after standing at 40 C. for some time was centrifugalized, the com- 

 plement remained in the supernatant fluid, as could be easily shown 

 by an experiment such as the one represented in the following proto- 

 col. 



EXPERIMENT TO SHOW THAT COMPLEMENT OR ALEXIN IS NOT ABSORBED BY 



UNSENSITIZED CELLS 



(4 c. c. of 5 per cent, emulsion of washed beef Llood. 

 0.8 c. c. of fresh normal goat serum (alexin or comple- 

 ment), not, by itself, hemolytic for beef blood. 



These substances are left together at 37.5 C. for one hour, then 

 centrifugalized into: 



I II 



Sediment of Cells. To this is added Supernatant Fluid (salt solution and 



inactivated serum of immune goat serum). To this is added washed 



which would cause hemolysis if beef blood and inactivated serum of 



alexin were present. immune goat containing heat stable 



element. 



Result = No hemolysis. Result = Complete hemolysis. 



Although, therefore, the red cells bind the thermostable specific 

 antibody of the immune serum and not the complement or alexin, 

 it was shown both by Bordet and by Ehrlich and his collaborators 

 that the red cells, after absorption of the thermostable substance, 

 when exposed to the action of the complement, were not only disin- 

 tegrated by hemolysis but, in the process, fixed or attached the com- 

 plement, so that this was no longer available for further activation 

 of other sensitized cells. 



The fact that the alexin or complement is used up during proc- 

 esses of lysis, as first described by Bordet, Ehrlich, and others, has 

 recently been made the subject of repeated investigation, srnce this 

 is out of keeping with the general enzyme or fermentlike nature of 

 complement indicated by many of its other properties. 



