PHAGOCYTOSIS 43 



Metchnikoff considers the subject of phagocytosis under three 

 aspects: i. Nutritional. 2. Resorptive. 3. Protective. 



Nutritional. Amoeba and certain other unicellular vegetable 

 organisms belonging to the myxomycetes possessing amoeba proper- 

 ties and having the faculty of throwing out pseudopodia or proto- 

 plasmic arms, acquire their food by enveloping smaller organisms, 



FIG. 1 6. Phagocytosis. Gonococci in leucocytes in pus from gonorrhoea. 

 (Kolle and Wassermann.) 



and other nutritious matter which they absorb. Certain intracellu- 

 lar ferments, which they possess, digest fibrin and gelatine, and con- 

 vert starch into sugar. These cells protect themselves against inim- 

 ical micro-organisms by enveloping and digesting them. V 



They are attracted by food and moisture (called positive chemo- 

 taxis) and repelled by strong solution of salt, poisons, etc. (negative 

 chemotaxis). ( 



Higher in the animal scale among the multicellular organisms, the 

 cells of the intestines have the property of absorbing and digesting 

 food. These fixed cells are called sessile phagocytes. Still higher 

 in the scale (man) certain digesting cells are present in the digestive 

 tract, which are incapable of absorbing food. They, however, 

 secrete ferments which digest gelatine and fibrin, and convert starch 



