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Ultrastructural changes of macrophages in mouse thymus during diges-tive process of exogenous material（heterophagy）and endogenous material（autophagy）were investigated with cytoehemieal demonstration of acidphosphatase（AcPase）activity.During the phagocytosis of maerophage

an apparent periodic change could be observed in the lysosomal system.According to this periodic change

we proposed a new concept of phago-cytosis period.This period could be divided into 2 stages

heterophago-eytosis stage and autophagocytosis stage.The main feature of heteropha-goeytosis stage was that the activity of phagocytosis was increased

a largenumber of irregular

s

haped（transformed）heterophagolysosomes（HPL）were formed

then many small lysosomes were formed by budding and pin-ching-off from the transformed HPL.In the autophagocytosis stage

a lotof small lysosomes were wrapped by the transformed HPL.It was shownthat in the autophagocytosis stage the autophagy of macrophage was a pha-nomenon of self-phagocytosis of HPL.