99. Connected with the subject of the nutrition of the fœtus and the changes which take place in the blood of it, may be mentioned certain recent discoveries[23], which would lead to the belief, that the function of the placenta is probably analogous to that of the liver during the intro-uterine life of the fœtus, and that the presence of bile in the blood of the placenta, discovered by modern chemists, is necessary to the maintenance of fœtal life (Breschet). 100. It is of the utmost importance to bear in mind the great distinction which exists between the independence of the fœtus, _quoad_ life, and its dependence, _quoad_ nutrition, in respect to the mother. The former state is secured by a total separation of the two circulations (maternal and fœtal). The latter by the close reciprocal contact of the organs of those circulations. Thence is it that we find the fœtus to live on, notwithstanding that its connection with the mother has been partially and sometimes even wholly, severed;—while on the other hand we cannot help admitting that, albeit this independence, the influence of the mother over the fabric of her offspring is unquestionable. 101. Here are two important positions. I have mentioned my experiments on the intact ova of the genus cat, (59,) to illustrate the first of them, and Dr. Prevost has since come to my assistance with as strong a case in further support of it[24]. This gentleman having observed an ovum still alive in the uterus of a ewe, which was a short time advanced in gestation, removed it and placed it upon a warm glass plate exposed to the rays of the sun, and attentively examined it with the microscope. The beatings of the heart became more lively. He noticed the blood arise to the surface of the chorion from the fœtus, there ramify plentifully, and by anastomosing vessels, return to two of the larger trunks which were the veins of the embryo. He concluded, therefore, that the ovum was an isolated substance.