[The vascular network and the perivascular spaces of the pars distalis of the hypophysis in developing chick embryos].

A quantitative analysis of the modifications undergone by the vascular networks and the perivascular spaces in the rudiment of the adenohypophysis has been carried out in normally developing chick embryos from the 7th incubation day to hatching. The present results point to the existence, during the developmental period mentioned, of a relationship between the extent of the capillary bed and, respectively, of the perivascular spaces, the gradual increment of the former being paralleled by a decrease of the latter. The rate of these events appears to be higher between the 14th and the 16th incubation days, namely when the vessels begin to acquire some of the morphological features typical of sinusoids, their thin walls getting gradually into closer contact with the secretory epithelial cells.