The chondroid tissue of the heart is an obligate provisional+ formation of the organ in question. It is formed during early stages of ontogenesis, develops maximally during the antenatal period and is preserved in the postnatal one. In a number of vertebrates it is the base for formation of cartilage and even bone in stroma of the heart. The ++chondroid tissue in embryos and fetuses performs, as regards the myocardium, stromal and trophic functions, further they are performed by the definitive connective-tissue stroma, in it vessels of the coronary system are situated. There are some reasons to suppose that the elements of the chondroid stroma are preserved during the postnatal ontogenesis in the myocardial intestinum, taking part in its metabolism.