We have before us the names of the nerves which connect the organs of speech with the organ of thought. Through some of the cranial nerves the mind immediately discharges its impulses upon certain organs, both consciously and subconsciously. This is illustrated by the motor occuli, patheticus, and abducens, which move the eye sometimes consciously and sometimes subconsciously. This shows that these nerves may, and often do, act upon the eye, without any conscious plan or purpose on the part of the individual.
The mind often manifests, through the cranial nerves, states of mind of which the person is unconscious. While consciousness is the power by which one knows his own states of mind, there is no proof that consciousness takes note of all one’s states of mind. The proof that it does not is found in the fact that people, through involuntary acts, often manifest mental activities of which they are unconscious. Spontaneous expression is truest.
The facial nerve causes the muscles of the face to portray the thoughts and feelings of the soul more truthfully than any artist could delineate them with pencil and brush. Before we can properly teach vocal culture and oratorical expression we must understand the principle of spontaneous manifestation by means of cranial nerves as distinct from purposeful forms of expression. The facial nerve not only acts as a motor of expression through the face, causing it to reveal thought and emotion, but acts in the same manner upon the tongue, causing it to form and modulate tones in song and speech.
Again note the nature of the hypo-glossal cranial nerve, which is not only a motor of the tongue, causing it to act spontaneously, but is distributed also to the muscles of the neck which are concerned in the movements of the larynx. The purpose of this distribution is probably to associate the action of the tongue with that of the larynx which is necessary for articulate speech. All the motions of the tongue are performed through the medium of these nerves.
The drawing exhibits the cerebral connection of all the cerebral nerves except the first. It is from a sketch taken from two dissections of this part. D. Posterior optic tubercle. The generative bodies of the thalamus are just above it. E. Cerebellum. H. Spinal cord. I. Tuber cinereum. K. Optic thalamus divided perpendicularly. W. Corpus restiforme. X. Pons Varolii. b b. Optic nerves: this nerve is traced on the left side back beneath the optic thalamus and round the crus cerebri. It divides into four roots; the first (g g) plunges into the substance of the thalamus, the next runs over the external geniculate body and surface of the thalamus, the third goes to the anterior optic tubercle, the fourth runs to D, the testis or posterior optic tubercle. C. Third pair common oculo-muscular, arising by two roots like the spinal roots of the spinal nerves, the upper from the gray neurine of the locus niger, the lower from the continuation of the pyramidal columns in the crus cerebri and Pons Varolii, p t. d, Fourth pair, apparently arising from the inter-cerebral commissure (I c), but really plunging down to the olivary tract (o t) as it ascends to the optic tubercles. e m. Motor or non-ganglionic root of the fifth pair, arising from the posterior edge of the olivary tract. e. Sensory root of the fifth pair running down between the olivary tract and restiform body to the sensory tract. f. Sixth pair, or abducens, arising from the pyramidal tract. g. Seventh pair, facial nerve, or portio dura, arising by an anterior portion from the olivary tract and by a posterior portion from the cerebellic fibers of the anterior columns as they ascend on the corpus restiforme, W. h. Eighth pair, portio mollis, or auditory nerve, with its two roots embracing the restiform body. i. Ninth pair, or glosso-pharyngeal; and j. Tenth pair, or par vagum, plunging into the restiform ganglion. J J. Fibers of the optic nerve plunging into the thalamus; immediately below these letters is the corpus geniculatum externum. k. Eleventh pair, or lingual nerve; the olivary body has been nearly sliced off and turned out of its natural position; some of the filaments of the lingual nerve are traced into the deeper portion of the ganglion, which is left in its situation; others which are the highest are evidently connected with the pyramidal tract.
The course and distribution of the Hypoglossal or Ninth pair of nerves; the deep-seated nerves of the neck are also seen: 1, the hypoglossal nerve; 2, branches communicating with the gustatory nerve; 3, a branch to the origin of the hyoid muscles; 4, the descendens noni nerve; 5, the loop formed with the branch from the cervical nerves; 6, muscular branches to the depressor muscles of the larynx; 7, a filament from the second cervical nerve, and 8, a filament from the third cervical, uniting to form the communicating branch with the loop from the descendens noni; 9, the auricular nerve; 10, the inferior dental nerve; 11, its mylohyoidean branch; 12, the gustatory nerve; 13, the chorda tympani passing to the gustatory nerve; 14, the chorda tympani leaving the gustatory nerve to join the submaxillary ganglion; 15, the submaxillary ganglion; 16, filaments of communication with the lingual nerve; 17, the glosso-pharyngeal nerve; 18, the pneumogastric or par vagum nerve; 19, the three upper cervical nerves; 20, the four inferior cervical nerves; 21, the first dorsal nerve; 22, 23, the brachial plexus; 24, 25, the phrenic nerve; 26, the carotid artery; 27, the internal jugular vein.