The Weight of the Ventricles in the Later Weeks of Intra-Uterine Life

In 1883 Muller published a survey of heart weights of feetuses, children of different ages, and adults, and his values have been the standard reference for over half a century (Brock, 1932). Muller's series included 61 stillborn babies ranging in size from 100 g. body weight to 3000 g. In his two groups that include infants with a body weight of 100-1000 g., he shows a low R.V./L.V. weight ratio with the left ventricle heavier than the right in three of the four readings for these age groups. The R.V./L.V. weight ratio became greater than unity in his heaviest group of foetuses (i.e. those weighing 3000 g. and more). Muller's method of dissection has since been questioned (Dull, 1941; Hort, 1955) because he weighed the free ventricle wall and the septum separately. He divided the weight of the septum in the constant proportion 30 per cent to the right side and 70 per cent to the left. This gives an erroneous impression of right and left ventricular weights as the proportion of each ventricle taking part in the formation of the septum alters with the relative sizes of the cavities (Fig.