8d passes through the front end of the medulla, and shews the roots of the seventh pair of nerves, and the overlapping of the medulla by the cerebellum.
Plate 17.
Complete List of Reference Letters.
vii. a. Anterior branch of seventh nerve. ar. Anterior root of spinal nerve. auv. Auditory vesicle. cer. Cerebrum. ch. Notochord. ch. Epithelial layer of choroid membrane. gl. Glossopharyngeal nerve. vii.hy. Hyoid branch of seventh nerve. hym. Hyaloid membrane. ll. Lateral line. v. mn. Ramus mandibularis of fifth nerve. vii. mn. Mandibular (spiracular) branch of seventh nerve. v. mx. Ramus maxillæ superioris of fifth nerve. nl. Nervus lateralis. ol. Olfactory pit. op. Eye. v. opth. Ramus ophthalmicus of fifth nerve. pch. Parachordal cartilage. pfal. Processus falciformis. pp. Head cavity. pr. Posterior root of spinal nerve. rt. Retina. sp. Spiracle. v. Fifth nerve. vii. Seventh nerve. vc. Visceral cleft. vg. Vagus nerve. vg.br. Branchial branch of vagus. vgcom. Commissure uniting the roots of the vagus, and continuous with commissure uniting the posterior roots of the spinal nerves. vgr. Roots of vagus nerves in the brain. vgin. Intestinal branch of vagus. vh. Vitreous humour.
Fig. 1. Diagram of cranial nerves at stage L.
A description of the part of this referring to the vagus and glossopharyngeal nerves is given at p. [426]. It should be noticed that there are only five strands indicated as springing from the spinal cord to form the vagus and glossopharyngeal nerves. It is however probable that there are even from the first a greater number of strands than this.
Fig. 2. Section through the hinder part of the medulla oblongata, stage between K and L. Zeiss A, ocul. 2.
It shews (1) the vagus commissure with branches on one side from the medulla: (2) the intestinal branch of the vagus giving off a nerve to the lateral line.
Fig. 3. Longitudinal and vertical section through the head of a Scyllium embryo of stage L. Zeiss a, ocul. 2.
It shews the course of the anterior branch of the seventh nerve (vii.); especially with relation to the ophthalmic branch of the fifth nerve (v. oth).