Ganglionic character of mesencephalic trigeminal neurons in the turtle Mauremys caspica.

A study of the morphology of the mesencephalic trigeminal neurons and their arrangement in the optic tectum has been made in the turtle Mauremys caspica employing the Cajal reduced silver method. The ganglionic features of its neurons suggest that the mesencephalic trigeminal nucleus (MTN) is a diffuse sensory ganglion located in the central nervous system. The different distribution of two cell populations, probably as a result of a distinct embryonic origin of their elements, and the atypical pattern of the ependyma lying underneath the MTN are discussed.