An experimental enquiry into the nature of the substance in serum which influences phagocytosis

Abstract

Metchnikoff, and his school, in the face of much opposition, lasting many years, have offered convincing proofs of the importance of phagocytosis in the protection of the animal body against bacterial invasion. The main theses of the Metchnikovian theory are now almost universally accepted, but the exact mechanism of the processes involved is even now the subject of keen controversy. If a highly virulent organism is injected into a susceptible animal, the leucocytes appear to be repelled, and to be unable to deal with the microbe, which multiplies and causes the death of the animal. If, however, the suitable immune serum is injected into the animal before inoculation, the phagocytes attack and devour the invading micro-organisms. Much discussion has centred round the interpretation of such experiments. The early work of Nuttall and others on the bactericidal action of normal serum, and Pfeiffer’s demonstration of the bacteriolysis of cholera and typhoid bacilli by immune sera in the absence of cells, formed the chief basis on which rested the humoral theory, which attributed the protection in such cases to the destructive action of the serum on the microbes. Flügge graphically illustrated the view of the humoralists by likening the phagocytes to the trenches made ready behind the fighting line to receive the conquered dead.