File:Johnston1907 fig020.jpg

Summary

FIG. 20. Reconstruction of the brain and cerebral nerves in a 12 mm. pig embryo. (From Minot's " Laboratory Text-Book of Embryology." Drawrt and revised by F. T. Lewis.)

Nerves." 3, oculomotor. 4, trochlear. 5, trigeminal, with its semilunar ganglion, s-l, and three branches, oph., ophthalmic; mx., maxillary; md., mandibular. The motor portion, which goes with the mandibular branch, is concealed in this view by the sensory portion. 6, abducens. 7, geniculate ganglion of the intermedius. Fibers from this ganglion mix with the motor fibers of the facial nerve, so that both sensory and motor fibers are found in the three branches, /. s. p., large superficial petrosal; ch. ty., chorda tympani; /a., facial. 8, acoustic, showing an upper vestibular portion, and a lower cochlear portion. 9, glossopharyngeal with its superior ganglion, s, above; its petrosal ganglion, p, below; and its three branches, ty., tympanic; /. r., lingual ramus; ph. r., pharyngeal ramus. 10, vagus, with its jugular ganglion, /, extending posteriorly as a ganglionic commissure, com.; and below, its ganglion nodosum, n. Its branches form the laryngeal plexus,beyond which is the recurrent nerve, rec. Just below the jugular ganglion is the auricular branch of the vagus. II, accessory, which joins the vagus; ex., its ramus externus. 12, hypoglossal. P., Froriep's hypoglossal ganglion. C. I, C. 2, C. 3, cervical nerves.

Brain and Sense Organs. Telen., telencephalon. Dien., diencephalon. Mesen. r mesencephalon. Meten., metencephalon. Myelen., myelencephalon. H., hemisphere. Ven. IV., roof of the fourth ventricle. Op., optic cup. L, lens. Na., nasal pit. Ot., otocyst.