VASCULAR SYSTEM.
The circulating system presents several peculiarities: 1st. In the heart; there is a communication between the two auricles by means of the foramen ovale. 2d. In the arterial system; there is a communication between the pulmonary artery and descending aorta, by means of a large trunk, the ductus arteriosus. 3d. Also in the arterial system; the internal iliac arteries, under the name of hypogastric and umbilical, are continued from the fetus to the placenta, to which they return the blood which has circulated in the system of the fetus. 4th. In the venous system; there is a communication between the umbilical vein and the inferior vena cava, called the ductus venosus.