Historical sketch on Immunity 539 



The theory of phagocytosis seeks to establish the part played by 

 these cells in the destruction of micro-organisms. It maintains that 

 the vital manifestation of the phagocytes, irritability, mobility, and 

 voracity, constitutes an essential factor in ridding the animal of 

 micro-organisms, because the true bactericidal ferment is contained 

 within the phagocytes, except in cases of phagolysis. The destruction 

 of the micro-organisms follows the laws which govern the absorption 

 of formed elements in general. This absorption, finally, is the work 

 of two soluble digestive ferments, one of which (fixative) is readily 

 excreted by the phagocyte into the plasmas of the blood and exuda- 

 tions. The theory of phagocytosis seeks to establish these principles 

 with the greatest possible exactness, but it has not yet ventured to 

 penetrate more deeply into the phenomena of intracellular digestion 

 which are confounded with the action of soluble ferments in general. 

 This problem is still far from being satisfactorily solved. 



In spite of very numerous objections, of which the principal ones [563] 

 have already been mentioned, the theory of phagocytosis, within the 

 limits indicated, so far from being overturned, has become more and 

 more consolidated, thanks to the numerous observations made since 

 its foundation. It is for this reason that the opposition has calmed 

 down of late years and that in many works the opinions expressed 

 have become more favourable to the role of phagocytosis in immunity. 



Soon after the Congress of Hygiene in 1891, the Pathological Society 

 of London devoted several meetings to a discussion of the question of 

 immunity. Many eminent observers took part in these debates, which 

 were, in general, favourable to this theory of phagocytosis 1 . 



At the International Congress of Hygiene, held at Budapest in 

 1894, the question of immunity was again discussed. Buchner 2 made 

 a report in which he specially insisted on the leucocytic origin of the 

 alexins, regarding this fact as particularly capable of reconciling the 

 bactericidal property of the body fluids with the theory of phagocy- 

 tosis. The alexins, however, secreted by the leucocytes, must, it was 

 assumed, carry out their principal function in the plasmas of the 

 blood and exudations. Phagocytosis would only intervene secondarily 

 for the purpose of ingesting the micro-organisms which had been 

 already killed or seriously injured by the alexins of the body fluids. 



1 Brit. Med. Journ., London, 1892, VoL i, pp. 373, 492, 591, 604. A very short 

 summary of this discussion was given in the DeutscJw med. Wchnschr., Leipzig, 

 1892, S. 296. 



a Munchen. med. Wchnschr., 1894, S. 717. 



