1. There is no definite limit between medulla oblongata and spinalis morphologically.
2. As there is always the anterior root of the 1st cervical nerve, the line of its upper end is used for the classification of the bulbar and spinal roots of the accessory nerve.
3. The bulbar roots are fine and long, but not very numerous, their number oscillates between 1 and 6 in 39 sides among 57, the most numerous specimen has 14 roots.
4. After Aoyagi the bulbar roots converge to a single bundle uniting with the upper end of the jugular ganglion. Such form is rather seldom in our specimens.
5. The spinal roots are always thicker than the bulbar, their number oscillates between 2 and 7 in 59-sides among 74, the most numerous one has 13 roots. There is one specimen which has no spinal root beginning the accessory from the second dorsal root.
6. The caudal end of the spinal roots is most frequently in the height of the 3rd to 5th cervical nerve, the most caudal height is at the 6th, the most cranial at the 2nd. This height and the form are not very symmetrical.
7. There are one ganglionic node at the junction of the 1st cervical root and accessory or a little cranial in 24 among 39, or in 33 sides among 74.
8. The dorsal root of the 1st cervical nerve is always thinner than that of the 2nd, its absense is observed in 31 among 74 sides (41.9%), When it exists there is only one bundle in 37 among 43.
9. In 6 specimens the dorsal root of the 1st cervical nerve converges to the accessory, in 3 among 6 the neighboring roots of that dorsal root are defined as the spinal roots after their form and position rather than the 1st cervical.
10. The correlative relation between the accessory and the dorsal root of the 1st cervical nerve, when it exists, may be classified in the following 4 forms.
I The dorsal root of the 1st cervical nerve is independent, although there may be any connecting anastomosis between it and accessory or that of the second cervical. 14 among 74 (18.9%).
II The dorsal root of the 1st cervical passes over to the accessory not reaching the medulla. 17 (23.0%)
III The dorsal root of the 1st cervical arising from the medulla passes over to the accessory so that it is deficient peripheral part. 6 (8.1%).
IV The dorsal root of the 1st cervical is replaced by that of the 2nd. 6 (8.1%).
11. Compared with the cases of Kazzander and Weigner in our Japanese fetuses the dorsal root of the 1st cervical nerve is defect more frequently, when it exists, it is poorer and often replaced by the accessory nerve.

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1) The differentiation of the brain wall of man begins at the rhombencephalon, especially at the somato-motoric part of matrix in the height of the facialis and abducens.
2) This differentiation of the neural tube corresponds to the Kahle's beginning exhaustion, Such structure is not to be seen in the other parts of the brain wall of XV developmental stage.
3) Except this part in the rhombencephalon there appears the second migration succeeding the first. In this developmental horizon it seems to appear also the medial longitudinal fascicle from the midbrain to medulla spinalis.
4) In the same horizon XV the beginning migration is observed at the basal lamina of the midbrain, where the occulomotor nerve sprouts. This migration is more advanced at its cranial part and most advanced at the subthalamus where the second migration is beginning, while in the caudal part of the midbrain the 1st migration is yet poor.
5) In the next XVI developmental stage there appears peripheral and central compact nerve bundel of thetrochlearis.
6) The nucleus n. trochlearis can be destined at the caudal continuation of the oculomotor nucleus which may be called advanced migration in this horizon.
7) The condition of the beginning exhaustion of the matrix at the height of facialis and abducens is advancing slowly while these 2 nerve roots approach to each other. In the earliest stage the abducens is 1 neuromere long caudal to the facialis.
8) In this horizon XVI there appears tractus solitarius which begins from the caudal part of the facial root in the 1st migration layer near the marginal fiber layer, which soon comes into it where it prolongs in compact bundle to the dorsal bundle of the 1st cervical segment.(Fig. 8, 11, 12, Pl. 2)
9) In the horizon XVII stage the mesencephalic and spinal tract of the trigeminal nerve, the solitar tract are distinct in the mass of the 1st migration layer of the differentiating nerve cells. The formers are not so compact as the latter.
10) The solitar tract in the mantle layer lies deeper and deeper from the marginal fiber layer in the succeeding stages.
11) In this horizon XVII there appears the 2nd differentiation layer at the basal lamina of the mesencephalon which may form the oculomotor nucleus. The same condition, though much feebler, is visible at its median part. On the position of the trochlear nucleus there is no 2nd layer yet. the trochlear root prolongs cranialward into the midbrain from the later periode of XVII up to XVIII.
12) The development of the cerebellum is very poor in these earlier developmental horizons. Its swelling and its inferior peduncle begin to become remarkable in the horizon XVII, the inferior cerebellar peduncle is discernible lateral to the spinal tract of trigeminal nerve and solitary tract.
13) The inferior cerebellar peduncle goes through the cell mass of the stato-acoustic nerve at the floor of the lateral recess, the dorsal part of the mass may become the vestibular, the ventral the cochlear nerve nucleus.
14) The exhaustion of the matrix in the height of facialis and abducens is very much advanced and the roots of both nerves come in the same level in the later stage of the horizon XVII. In the next horizon XVIII the matrix becomes still, wandering the nucleus n. facialis ventro-lateral, the remaining part becomes nucleusn. abducens.
15) The motor nucleus of the trigeminus is very early discernible in the mantle layer at the lateral part of the basal lamina continuing to portio minor. To it the cell mass of the medial part of that lamina must be added in later stage, the horizon XVII, and it may proceed rapid becoming almost independent at the same horizon with that of the abducens.
17) The perforation of the foramen Magendi and Luschka does not occur till the horizon XVIII developmental stage.

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