[Quantitative study of the heart in 2 human twin embryos at 14 mm C-R (stage 18)]

Two hearts of human twin embryos at 14 mm C-R (stage 18) were studied by means of light microscopy and quantitative methods. The serial sections of the embryos, 5 micron thick, were projected by using a microprojector for the measurement of the cardiac diameters and cardiac profile areas. The calculated heart volumes were 8.34 and 8.45 mm3, respectively. Cardiac volume is more accurate than linear measurement to establish quantitative development of the heart. It can also be considered an accessory index for embryonic classification.