per i venous (per i venus)

[ What is called a per i visceral cavity may be one of four things: 1. A cavity within the mesoblast, more or le representing the primitive blastocœle. 2. A diverticulum of the digestive cavity, which has become shut off from that cavity (enterocœle). 3. A solid outgrowth, representing such a diverticulum, in which the cavity appears only late (modified enterocæle, or schizocæle). 4. A cavity formed by invagination of the ectoderm (epicœle). And whether any given per i visceral cavity belongs to one or other of these types can only be determined by working out its development. Huxley, Anat. Invert., p. 544.