The foetus has no communication with the open air, and the experiments made upon the lungs prove they have never respired; for they sink to the bottom when put in water: whereas those of infants who have breathed always float on the top; the foetus then does not respire in the womb, consequently it cannot form any sound by its voice; and therefore what has been related of the groaning and crying of children before their birth may be considered as fables. After the flowing of the waters it may happen, that the air has found an entrance into the cavity of the matrix, and then the infant may begin to respire before it is brought forth. In this case it may be able to cry, as the chicken cries before the shell of the egg is broken, which it can do from there being air in the cavity which is between the external membrane and the shell. This air is found in all eggs, and is produced by the internal fermentation of matters contained in them[AF]. [AF] See La Statique des Vegetaux, Chap. vi. The lungs of the foetus being without any motion, have no more blood enter into them than is requisite to nourish and make them grow; and there is another road opened for the course of its circulation. The blood in the right auricle of the heart, instead of passing into the pulmonary artery, and returning, after having ran through the lungs into the left auricle by the pulmonary vein, passes immediately into the left by an opening, called the _foramen ovale_, which is in the partition of the heart between the two auricles. It enters afterwards into the aorta, which distributes it by its ramifications, at going out of which the venous branches receive it, and bring it back to the heart by uniting all in the _vena cava_, which terminates at the right auricle of the heart. The blood which this auricle contains, instead of passing entirely by the foramen ovale, may escape in part into the pulmonary and the aorta by an arterial canal, which goes immediately from the one to the other. It is by these roads that the blood of the foetus circulates without entering into the lungs, as it enters into those of children, adults, and every animal which breathes.