Histolysis

HISTOLYSIS (from Greek histos-tissue and lysis-dissolution), destruction of tissue elements, both cells and intercellular substances, by their dissolution. H. is observed 1) in developmental processes associated with metamorphosis, 2) in pathological cases. A classic example of the first type of H. is the transformation of a caterpillar into a butterfly, occurring in the pupa stage; at this time all muscles and organs break down and dissolve, and in their place new ones are formed from imaginal disks. Another example is the atrophy of a tadpole's tail during its transformation into a frog, also accompanied by extensive destruction of muscles, with the disintegrated material being used by the rest of the organism. Around the disintegrating parts, an accumulation of white blood cells-phagocytes is observed, which, according to Metchnikoff's theory, play the main role in the process of H. and which destroy cells by phagocytosis-ingestion and intracellular digestion. At present, the role of phagocytosis is greatly limited, and the process of H. is explained by the appearance of special substances that dissolve tissues-lysins and peptic enzymes, also secreted by leukocytes (lyocytes, lyocytosis).-Examples of pathological H. can be inflammatory processes, e.g., the melting of tissues in the formation of an abscess. (See Phagocytosis, Lysins, etc.).