The mesencePhalic root of the trigeminal nerve has been previously investigated as regards its flbre constitution and its relation to neighbouring structures. The presence of collaterals from the root fibres as well as the axonal bifurcation
of the mesencephalic nucleus cells have been described bY Cajal (1896), Johnston (1909), Thelander (194?) and Kappers et al (1963). However, Cajal (1896) was the first to report that collaterals from the mesencephalic root travese to the
motor cells of the trigeminal nerve. The anatomical relationship between the intrabulbar part of the trochlear nerve and the mesencephalic root was described in different animal species by Duval (18?B), Obersteiner (1892), Hulles
(1907) and Weinberg (1928).