Ultrastructure of intramuscular haematomas and electron-probe x-ray analysis of extracellular and intracellular iron deposits.

Haematomas were produced in rabbits by intramuscular injections of autologous blood. Clotting and marked lysis of erythrocytes was noted in these haematomas but there was no evidence of fragmentation of erythrocytes, prior to, during, or after ingestion by macrophages as has been reported in other sites such as spleen, peritoneal cavity or joint cavity. The phagocytosis of intact erythrocytes, lysed erythrocytes and haemoglobin led to the formation of three main types of lysosomal bodies, (1) myelinosomes, (2) siderosomes and (3) myelinosidersomes. Electron-probe X-ray analysis of siderosomes has yielded further data supporting the idea that haemosiderin is essentially an inorganic iron compound; presumably a hydrated ferric oxide. An unusual and hitherto unreported finding was the occurrence of electron-dense granules in the connective tissue matrix in two animals. The granules were shown to contain iron, calcium, potassium and phosphorus. It is thought they might represent an attempt at pathological calcification in damaged tissue.