To make a midsagittal section, what we want to do is cut right down the longitudinal fissure and divide the brain on midline into two separate halves. Letâs take a look at the midsagittal section of the sheep brain. We can see the cerebrum, and this white structure is called the corpus callosum. The corpus callosum is a commissure, it consists of myelinated axons that connect the right and left cerebral hemispheres. Right below the corpus callosum is a lateral ventricle, thereâs a lateral ventricle on the right and on the left. They are lined with ependymal cells that circulate the cerebrospinal fluid found inside of them. This central region of the brain is called the thalamus. Right below the thalamus, this region is called the hypothalamus. This is the optic chiasm where some of the right and left optic nerve fibers cross midline. This round structure is the mammillary body, which is involved with the transmission of olfactory information. Here, is the pituitary gland. This is the pineal body which secretes one hormone, melatonin. Here we can see the transverse fissure that separates the cerebrum from the cerebellum and moving through the transverse fissure we can see we look right onto the dorsal surface of the midbrain, this projection is called the superior colliculus. Itâs part of the corpora quadrigemina. Taking a look at the anterior portion of the midbrain this region is a cerebral peduncle. Just inferior to that is a region called the pons, and just inferior to pons is the medulla oblongata. This is the cerebellum and you can see the white branching arbor vitae contained within the cerebellum. The fourth ventricle is right next to the cerebellum. The pons and the medulla make up the ventral wall of the fourth ventricle.