Cytological and cytochemical studies of the necrotic area of the bulbus of the chick embryo heart: phagocytosis by developing myocardial cells.

The muscular wall of the bulbus cordis of the chick embryo was studied by electron microscopy during H. H. stages 27--31. Results show that the muscle cells of the bulbus undergo necrosis during these stages. The morphology of dead cells in this area is similar to that described in other embryonic myogenic tissues. Although dead myocytes appear acid-phosphatase-negative, lysosomes may well be involved in this necrotic process as there is a significant number of cells with autolytic lesions among the neighbouring healthy muscle cells. The phagocytosis of the cell detritus resulting from the degenerative process appears to be carried out by neighbouring myocytes and by macrophages. The significance of these results is discussed both from the cytological and from the morphogenetic point of view.