The ›Œconomia Regni Animalis› is chiefly directed to a detailed analysis of the _blood_, the _brain_, and finally the _soul_. In this investigation SWEDENBORG directed his attention not only to the morphological and physiological aspects of the subject, but also to the _embryology_ of the organs; and he penetrated so deeply into the very essence of development, that, as Professor J. A. HAMMAR (Uppsala) has pointed out, he succeeded in arriving at a conception on this point, which was considerably better than that of his times. As is well known, during the first part of the eighteenth century the idea was generally prevalent that, when the organism developed from the egg or sperm, it grew forth out of it, much like a flower developes out of the bud, or, in other words, that the different organs existed pre-formed in the egg or sperm and that development consisted only in an extension of its size. SWEDENBORG expressed himself very decidedly against this ›pre-formation theory›: The development consisted by no means merely in a growth or expansion of the germ, (›seminis extensio›), or of a prototype of the future creature existent in the germ, (›non ... aliqua realis effigies maximi in minimo, seu in aliquo primo typus futuri corporis, qui simpliciter expanditur.› See Œc. R. A. I., No. 249); but there was in the germ a certain formative substance or power, by means of which the various parts of the embryo were developed one after the other, organ after organ. ( ... singula membra successive, seu unum post alterum producuntur ... Œc. R. A. I., No. 247). It will be seen that SWEDENBORG has here put forth essentially the same theory as was later presented by CASPAR FRIEDRICH WOLFF in his well known ›Doctorsdissertation› of the year 1759, _i. e._, the so called _theory of ›epigenesis›_. I shall here also discuss some of the results and conclusions, which SWEDENBORG arrived at in the ›Œconomia Regni Animalis›, concerning the _brain_ and _its function_.