184 ORIGIN OF COMPLEMENT AND IMMUNE BODY 



mechanism is due to lack of complement. It would, however, be 

 unwise to attach too much importance to this proof. 



The difficulties in coming to a conclusion on this subject are 

 great, but on the whole it would appear that the evidence is some- 

 what in favour of the views of Metchnikoff, and that in all proba- 

 bility there is no free alexin, or but little, in the plasma, and that 

 the main source of this substance is the polynuclear leucocyte, 

 but we cannot regard this as definitely proved. This being so, 

 the discussion as to whether the formation of alexin is a vital 

 secretory process or a phenomenon of cell death and solution 

 cannot be regarded as of great importance. Here again the 

 experimental work is most inconclusive, Lastchenko holding that 

 living leucocytes give off alexin when suspended in heated serum, 

 whilst Lazar found that it is only set free when some of the 

 leucocytes are destroyed. Kanthack's experiments may perhaps 

 be quoted at this point. He found that anthrax bacilli immersed 

 in frog's lymph become surrounded by eosinophile cells. After a 

 time these cells discharge their granules, and the bacilli soon 

 begin to show signs of injury, becoming less refractile and losing 

 their sharp-cut outline. After this these leucocytes move away 

 from the bacilli, from which we might argue that they are un- 

 injured, and that the solution of their granules is a vital action, 

 and exactly equivalent to the secretion of pepsin by the gastric 

 cells. This, of course, does not exclude the possibility that alexin 

 might also be liberated during the process of phagolysis, as 

 Metchnikoff maintains. 



As regards the origin of the immune body the evidence is unani- 

 mous, showing that it originates from the lymphoid tissues, and 

 probably from the mononuclear leucocytes. It is found that if 

 animals be injected with cholera vibrios, killed at varying intervals 

 afterwards, and extracts made of the different organs, the first sites 

 in which the antibodies make their appearance are the lymphoid 

 organs, especially the bone-marrow, spleen, and lymphatic glands. 

 Similar facts have been observed for other bacteria and for red 

 blood-corpuscles (Pfeiffer and Marx, Deutsch, Wassermann). And 

 in Bulloch's experiments the amount of haemolytic amboceptor was 

 found to run roughly parallel with the number of mononuclear 

 leucocytes present in the blood. In all probability this increase of 

 circulating mononuclears must be regarded in such cases as an 

 indication of the activity of the lymphoid organs, which are to be 

 regarded as the main source of the protective antibodies. This is 

 a generalization of the highest importance in immunity, and it is 



