COMPLEMENT FIXATION 183 



the end-piece remains free, complementary activity does not appear. 

 This explanation, however, is only hypothetical, is not entirely supported 

 by other experiments and fails to take into account the influence of salts 

 on colloidal suspensions and solutions. Excesses of salts also interfere 

 with the action of complement, but on dilution to isotonicity the function 

 is immediately restored. Therefore, the salts do no permanent injury 

 to complement. Hektoen and Reudiger, as well as Manwaring, offer 

 the explanation that ionization of the salt permits of a union with com- 

 plement which is easily reversible. Certain salts, such as those of 

 bile acids, as well as sodium oleate, permanently injure complement. 

 The salts are of themselves hemolytic, but serum, inhibits their hemo- 

 lytic activity. The amounts which are hemolytic in themselves com- 

 pletely inhibit complement and by virtue of the presence of serum 

 cannot produce lysis. 



Acids and alkalis in considerable concentration permanently destroy 

 complement, but if the injury be due to a dilute alkali the comple- 

 mentary activity may be restored by neutralization. It appears that 

 moderate concentrations of acids destroy complement without restora- 

 tion by neutralization. Dilute acids accelerate hemolysis and for this 

 reason are to be avoided in accurate work with complement fixation. 

 Certain protein products, such as urea (also urea sulphate) and guani- 

 din are anti-complementary. 



Colloids may also inhibit complement as, for example, the organic 

 colloids, glycogen, inulin, pepton, albumose, gelatin, etc., as well as 

 inorganic colloids, such as quartz sand, kaolin and carbon. Numerous 

 indifferent chemical precipitates, such as colloidal iron hydroxide and 

 protein precipitates inhibit complementary activity. It is possible that 

 in certain measure this may depend upon their interference with the 

 complement amboceptor and antigen behaving as interacting colloids. 



The influence of lipoids on complementary activity is of great im- 

 portance, particularly in the Wassermann test, but we may mention at 

 this point that lecithin, cholesterol, protagon and tristearin in sufficient 

 concentration are anti-complementary as well as certain lipins, including 

 the neutral fats, olive oil, triolein, etc. Added, finally, to the list of 

 chemical agents are boric acid, benzoic acid, formalin, sodium fluoride, 

 sodium sulphite and extracts of certain spices. 



Anti-complementary Action of Cells, Tissue Extracts and Body 

 Fluids. As was pointed out by von Dungern, most animal cells either 

 in the form of emulsions or cells may inhibit the activity of comple- 

 ment. Muir found that the stroma of red blood-corpuscles enters into 

 fixed combination with complement and that if washed red corpuscles 

 are heated to 55 C. for twenty-four hours they also will combine 

 directly. The union does not take place at o C. but occurs readily at 

 37 C. The combination is apparently not dissociable. Not only animal 

 cells but also a wide variety of bacterial emulsions or their filtrates 

 as well as yeast cells fix complement. On the basis of the Ehrlich 

 hypothesis this may be due to the union of complement with the com- 

 plementophile groups of those sessile receptors of cells which by im- 



