The Mesencephalic Nucleus of the Trigeminal Nerve in Young Snapping Turtles

The mesencephalic root of the trigeminal nerve is a constant feature of all gnathostomes. The cells of origin of these root fibers lie mainly within the midbrain. Peripherally the fibers are distributed to the musculature of the jaws, and they constitute the proprioceptive apparatus of that musculature (Corbin and Harrison, \u2740). Although the large mesencephalic V nucleus cells have been recognized for about 90 years (Meynert, \u2767), adequate descriptions of their size, numbers and distribution are still not great. Perhaps the most comprehensive study is that of Weinberg (\u2728) on fifteen different species in five of the classes of vertebrates. Among these was a turtle, Chrysemys marginata. The present study was undertaken to compare the mesencephalic V nucleus cells in the snapping turtle with the cells previously described in Chrysemys