l82 ORIGIN OF COMPLEMENT 



generally accepted as the source of the fibrin ferment. If the 

 complements are also set free during the solution of the leucocytes, 

 there should be far more present in the serum than in the circu- 

 lating plasma ; it might happen, indeed, that the plasma might be 

 devoid of any complementary action, though this does not neces- 

 sarily follow. 



The difficulty of investigating this subject is very great, and 

 the evidence is mostly indirect. As far as it goes, it seems to 

 point to the fact that the plasma is alexin-free, or, at any rate, 

 poorer than the serum. The main direct researches into this 

 subject are those of Gengou and Falloise, and here, again, they 

 point in a diametrically opposite direction. Gengou (whose results 

 have been accepted in their entirety by Metchnikoff) worked with 

 plasma obtained by preventing coagulation by collecting the blood 

 in paraffined tubes and centrifugalizing forthwith a method cer- 

 tainly less open to objections than any dependent on the addition 

 of anticoagulants, but difficult in execution. He found that plasma 

 thus prepared was devoid of bactericidal action, though the serum 

 from the same animal possessed it. In some cases the plasma 

 betrayed some action, perhaps because a partial coagulation had 

 taken place, but it was always less potent than the serum. These 

 results have been opposed by numerous investigators, using various 

 methods of inhibiting coagulation. Thus, Falloise used intra- 

 venous injections of peptone, the addition of sodium oxalate or 

 fluoride ; Petterson used oxalate and citrate, and Hahn histon, 

 and in all cases no appreciable difference in alexin content between 

 the plasma and serum was found. But this is hardly a fair test. 

 Peptone is generally believed to be a leucotoxic or leucolytic 

 agent ; and in the case of the citrated or oxalated blood it is 

 obvious that (if leucocytes are the origin of fibrin ferment) some 

 leucolysis has occurred, since the cell-free fluid coagulates on the 

 addition of calcium. Falloise also worked with paraffin tubes on 

 Gengou's method, and found that the plasma contained as much 

 haemolytic complement as the serum. Lastly, both he and 

 Lambotte worked with plasma obtained by centrifugalizing (or 

 by allowing sedimentation to occur in) the blood in a vein isolated 

 between two ligatures and kept at a low temperature, and with 

 the same results. Delezenne, however, criticizes these results by 

 pointing out that plasma obtained in this way coagulates instantly 

 in glass tubes at the ordinary temperature, a phenomenon in- 

 dicating that fibrin ferment is present, and that leucocytes have 



