PHAGOCYTOSIS 



"L'exsudat inflammatoire doit etre considere comme line reac- 

 tion centre toutes sortes de lesions et Fexsudation est un phenomene 

 plus primitif et plus ancien que le role du systeme nerveux et des 

 vaisseaux dans I'lnflammation." 6 



He compared the process of cell ingestion or phagocytosis of for- 

 eign particles, as here observed, to that taking place in the most 

 simple intracellular digestion which occurs in unicellular forms, a 

 hereditary cell function now specialized in certain mesodermal cells, 

 and passed on in the evolution of higher forms to other specialized 

 cells. And indeed in animals of the most complex structure the 

 leukocytes which carry on this phagocytic process may be considered 

 as, in a way, representing a primitive form of cell, since they are 

 only nucleated elements of the body which wander from place to 

 place, and are anatomically independent of nervous control. In 

 1883, at the Naturalists' Congress in Odessa, Metchnikoff 7 first 

 expressed his views and communicated the first of the splendid re- 

 searches upon which our modern conception of phagocytosis is based. 



His earlier studies were carried out with a small crustacean, the 

 daphnia, in which he studied the reaction which followed the intro- 

 duction of yeast cells. He observed the struggle which ensued be- 

 tween the ameboid leukocytes of the crustacean and the infecting 

 agents and determined that complete enclosure of the yeast within 

 the leukocytes assured protection to the daphnia, while a failure of 

 this process, either from fortuitous causes or because of too large a 

 quantity of the infecting agents, resulted in disease and rapid death. 



This early work of Metchnikoff forms the beginning of a long 

 train of investigations to which we owe most of the basic facts we 

 possess concerning the role of the phagocytic cells in the protection 

 of the body against infection. Just as the various serum phenomena, 

 of which we have spoken, have a general biological significance apart 

 from their importance in relation to bacterial invasion, so the process 

 of phagocytosis must be looked upon as an attribute of the animal 

 and vegetable cell which has important physiological bearing entirely 

 apart from infection. 



In fact, the ingestion of bacteria and other foreign particles by 

 the leukocytes and other phagocytic cells of higher plants and ani- 

 mals is entirely analogous to the intracellular digestive processes 

 which take place, as the ordinary manner of nutrition, among the 

 unicellular forms. Among the rhyzopods, in general, food is taken 

 in by means of the ingestion of other smaller forms of life, bacteria, 



6 Inflammatory exudation should be considered as a reaction against all 

 sorts of injuries, and exudation is a phenomenon more primitive and ancient 

 than are the parts played by nervous system and blood vessels in the process 

 of inflammation. 



7 Metchnikoff. Arb. a. d. zool. Inst., Wien, Vol. 5, 1883. 



