INFLAMMATION AND PHAGOCYTOSIS 135 



more to be regarded as inflammation, says Cantacuzene with 

 justice, than the congestive phenomena which accompany 

 ovulation or precede coitus can be called fertilisation. 



Phagocytes, phagocytosisanddigestion. — Metchnikoff 

 has given the name of phagocytes to those cells which are 

 capable from their own activity of seizing and incorporating 

 solid particles. (There is no question here of the faculty of 

 absorbing substances in solution.) 



Certain phagocytes are migratory cells : for example the white 

 corpuscles of the blood. Others are fixed cells — for example 

 many of the endothelial cells of the blood-vessels and lymphatics, 

 the endothelial cells of the omentum and the neuroglia 

 cells. Others originally motile may become fixed at a certain 

 period in their existence. 



The fundamental property of phagocytes is intracellular 



digestion. 

 MetchnikofiPs first observations were on the property of 

 intracellular digestion in the intestinal epithelium of a great 

 many Turbellarians. In the Coelenterata and the Sponges 

 digestion is intracellular, i.e., the nutritive particles instead of 

 being digested in a cavity with the help of juices poured out 

 by digestive cells undergo digestion in the interior of the cells 

 themselves. 



The Metazoa have inherited this property from the Protozoa. 

 Originally all the cells of the inferior Metazoa are capable of 

 phagocyting ; there are both ectodermic and endodermic pha- 

 gocytes ; later the function devolves entirely on specialized 

 cells belonging to the mesoderm. 



The phagocytic cells of man are descendants of cells whose 

 normal function was to digest intracellularly, and through them 

 we still possess this method of digestion, side by side with the 

 extracellular digestion which occurs in our stomach and 

 intestine. 



Phagocytosis is thus a function very wide-spread among 

 living beings, and the struggle against infection is only a 

 particular case of it. 



" The phagocytes are those cells which have best preserved 



