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From this it will be understood that in the human embryo, and in the embryos of animals in which the communications are not closed, the same thing happens, namely, that the heart by its motion propels the blood by obvious and open passages from the vena cava into the aorta through the cavities of both the ventricles, the right one receiving the blood from the auricle, and propelling it by the pulmonary artery and its continuation, named the ductus arteriosus, into the aorta; the left, in like manner, charged by the contraction of its auricle, which has received its supply through the foramen ovale from the vena cava, contracting, and projecting the blood through the root of the aorta into the trunk of that vessel.

This woman had shown no symptoms of the malformation. There were also hearts in which the interventricular septum was deficient, the ductus arteriosus patent, or some valvular malformation present. All these persons had reached puberty. Displacements of the heart are quite numerous. Deschamps of Laval made an autopsy on an old soldier which justified the expression, "He had a heart in his belly."

And this is so, because in the foetus, as already said, whilst the blood is not passing through the lungs from the right to the left cavities of the heart, it flows by the foramen ovale and ductus arteriosus directly from the vena cava into the aorta, whence it is distributed to the whole body. Both ventricles have, therefore, the same office to perform, whence their equality of constitution.

The organs of circulation undergo the following changes after birth, and the extent to which these changes have advanced will give an idea of how long the child has lived: The ductus arteriosus begins to contract within a few seconds of birth; at the end of a week it is about the size of a crow quill, and about the tenth day is obliterated.