The "septum pellucidum" has been described since antiquity. Even though people such as Vicq d' Azyr (12) and Burdach (3) pictured the septal region in their drawings, the nuclei associa­ ted with the pellucidum--the septal nuclei--were not described until Meynert (10). Since Meynert's description, this portion of the limbic system has been troublesome in terms of nomenclature. Scientists about the turn of the twentieth century proposed quite diverse termin­ ologies. For example, Elliot Smith first wrote of the precommis­ sural area (4) and then later of the paraterminal body (5). These terms, however, were meant to extend beyond the septal nuclei of our understanding. Unger (11) and Herrick (8) proposed the familiar terms--nucleus lateralis septi and nucleus medialis septi; but again they were somewhat broader in definition than is accepted for current usage. These terms, however, were rejected by Johnston (9). In Johnston's great paper, he pointed out that the hippo­ campus seems to evolve out of large portions of the septal nuclei. It was appropriate then to borrow a term previously used by Elliot Smith (6), but in another context--primordium hippocampi. Johnston's primordium hippocampi corresponds to the lateral septal nucleus of current usage. He introduced the terms medial and lateral parolfactory area to refer to the remaining portions of the septal nuclei of Herrick (8). Hence, the lateral parol factory area refers to the nucleus accumbens septi of Ariens Kappers (2).