Stereotaxic operations via the foramen magnum in the rat

An inexpensive stereotaxic apparatus is described which can be used to insert an instrument percutaneously into the rat's brain via the foramen magnum and so avoid either a skin incision or a burr-hole in the skull. The caudal part of the brain from the inferior colliculus dorsally, to the medullary corticospinal tract ventrally, can be reached in this way and the relative merits of the method are dicussed.