. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. THE MEDULLA. 95 the Accessorms (Fig. 43): a nerve which left the same cell-column farther posterior; also a part of the motor vagus root (Fig. 46) presents a similar thing. We now come to the two nerves which arise from the major part of the cell-column under consideration: viz., the Facialis and the motor Trigeminus. Both are not always sharply differentiated from each other in the region of the roots. In the lower vertebrates the motor Facialis is usually much smaller than
. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. THE MEDULLA. 95 the Accessorms (Fig. 43): a nerve which left the same cell-column farther posterior; also a part of the motor vagus root (Fig. 46) presents a similar thing. We now come to the two nerves which arise from the major part of the cell-column under consideration: viz., the Facialis and the motor Trigeminus. Both are not always sharply differentiated from each other in the region of the roots. In the lower vertebrates the motor Facialis is usually much smaller than the masseteric branch of the Trigeminus, prob' ably because the face-musculature is less developed. Fig. 49 shows the posi- tion of the Facialis and of the nucleus of the Abducens in the alligator and in Fig. 50 is presented a section which cuts the motor column at a higher level when it dilates in the dorsal portion for the nucleus of the Trigeminus. The nucleus of the Facialis is not a single structure. In the longitudinal as well as in the antero-posterior direction it shows interruptions. For. Fig. 51.—Lacerta agilis. Region of exit of the Trigeminus {'). that reason one might easily designate in different animals different cell- groups as the origin of the nerve. But all of these cell-groups belong to the same mass of great multipolar cells, whose neuraxons pass into motor nerves. At the anterior end of the medulla the gray mass which received the sensory nerves on the latero-dorsal aspect becomes again very much en- larged. At this point the Trigeminus nerve enters it. In this frontal sensory nucleus of this nerve only a part of the fibers from the Gasserian Ganglion end, while a greater part turn toward the spinal cord, there to gradually enter the gray matter, which we see in all sections from the ujDper end of the spinal cord to the entrance of the Trigeminus into the medulla. This descending portion has been described as the hulho-spinal root of the Trigeminus.
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