Abstract
1) After administration of large quantities of fat and vitamin A to rats in the last stage of gestation, transition of these substances to the fetal side of the placenta was observed.
2) Fat does not pass through the placenta after its decomposition by lipase but in the original form of fat in fine granules.
3) Vitamin A is kept in reserve in the placenta and apparently also in the yolk sac.
4) The Langhans cells in the chorionic epithelium does not play a part in the transition of fat and vitamin A through the placenta. These substances pass through the interspaces between these cells.
5) Both fat and vitamin A whether administered to the maternal or the fetal side, were found detained in the basal layer.
6) Only small quantities of fat and vitamin A pass over into the chorionic stroma and a transport route via the extra-vascular aqueducts could not be established.
7) No intraplacental transformation of carotene into vitamin A could be observed.
