III. On the commissures of the cerebral hemispheres of the marsupialia and monotremata, as compared with those of the placental mammals

As it is most convenient to pass from the best to the least known, and especially as the terms used in describing the anatomy of the vertebrated animals have in most cases been originally bestowed upon parts of the human body, the Paper commences by a short description of the septum ventriculorum and commissures of the human brain. This is done with a view to establish clearly, both by their structure and development, the mutual relations of the great transverse commissure or corpus callosum and the fornix. The latter is defined as essentially a longitudinal commissure, consisting of two lateral halves closely applied for a short space in the middle line, but each half belonging to its own hemisphere, and formed out of the longitudinal fibres bordering the superior margin of the ventricular aperture.