[Morphometric studies of rat myocardium during early postnatal period].

The mass development of heart ventricle (right and left with septum) was investigated with histologic-morphometric methods on rats from 1...14 days of live. The increase (twice) of myocard area is caused by increase of myocards of the left ventricle. Growth is the result of hyperplasie, in the second week it is the result of hypertrophy of heart muscle cells. The number of interstitiell cells enlarges to more than once. The perinatal change of circulation is the decisive factor for postnatal heart growth.