It has been thought that the blood of the mother passes into the body of the foetus, by means of the placenta and umbilical cord. It was supposed that the sanguinary vessels of the matrix opened into the vacuities, and those of the placenta into the nipples, and that they joined one to the other; but experience is quite contrary to this opinion; for if the arteries of the umbilical cord is injected the liquor returns by the veins, and not any part of it escapes externally. Besides, the nipples may be drawn from the vacuities where they are lodged, without any blood issuing either from the matrix or placenta: a milky liquor only issues from both, and which, we have already observed, serves the foetus for nutriment. This liquor possibly enters into the veins of the placenta, as the chyle enters into the subclavian vein; and perhaps the placenta in a great measure performs the office of the lungs in bringing the blood to maturity. It is certain that the blood appears much sooner in the placenta than in the foetus, and I have often observed in eggs that have been under the hen for a day or two, that the blood appeared at first in the membranes, and that their sanguinary vessels are very large and numerous, while the whole body of the chicken, excepting the point where these blood-vessels terminate, is only a white and almost transparent matter, in which there is not the smallest sign of a sanguinary vessel. It has been imagined, that the liquor of the amnios is a nutriment the foetus receives by its mouth. Some naturalists pretend to have observed this liquor in the stomach, and to have seen some foetuses to which the umbilical cord was entirely wanting, and others who had but a very small portion, which did not at, all adhere to the placenta; but in this case might not the liquor have entered into the body of the foetus by the small portion of the umbilical cord, or by the umbilical vessel itself? Besides, to these observations we may oppose others. Some foetuses have been found whose lips were not separated, and others without any opening in the oesophagus. To conciliate these circumstances, some anatomists have thought that the aliments passed into the foetus partly by the umbilical cord, and partly by the mouth: none of these opinions appear to have any foundation. It is not the question to examine the growth of the foetus alone, and to seek from whence and by what it draws its nutriment, but how the growth of the whole is made; for the placenta, liquor, and membrane increase in size as well as in the foetus; and consequently the instruments and canals employed to receive or carry this nutriment to the foetus, have a kind of life themselves. The expansion of the placenta and membranes is as difficult to conceive as that of the foetus; and we might say, with equal propriety, that the foetus nourishes the placenta, as that the placenta nourishes the foetus. The whole mass is floating in the matrix, and without any adherence at