Corticoseptal projections in the snakes Natrix sipedon and Thamnophis sirtalis

The projections of the cerebral cortex upon the septum in water snakes (Natrix sipedon) and garter snakes. (Thamnophis sirtalis) were studied with the Fink-Heimer degeneration techniques. Two cortical areas send major projections to the septum. Medial cortex projects bilaterally to the dorsal portion of the precommissural septum along its full rostrocaudal extent. The ipsilateral projection is more massive than the contralateral one. Dorsal cortex projects ipsilaterally to a column within the septum which is present dorsally, caudal to the level of the anterior commissure, but shifts ventrally as the septum is followed rostrally. Lateral cortex may send a sparse projection to the ipsilateral ventral septum.