Canine Brain Section

The mesencephalon (midbrain) is at the center of this transverse section through a canine brain. Notice the mesencephalic aqueduct near the center of the midbrain. Rostral colliculi occupy the tectum, the region dorsal to the aqueduct. The fiber bundle at the ventral surface of the midbrain is crus cerebri. Substantia nigra is dorsal to the crus and further dorsal is midbrain tegmentum. (The bilateral gray "ears" are medial geniculate nuclei of the diencephalon.).