156 THE ORIGIN OF VERTEBRATES 
muscles from the cranium to the shoulder-girdle, innervated by the 
XIIth (hypoglossal) nerve. The ventral series of segments give 
origin to the musculature supplied by the trigeminal, facial, glosso- 
pharyngeal, and vagus nerves. 
Also, the afferent or sensory nerves of the skin over the whole of 
this head-region are supplied by the trigeminal nerve, while the 
afferent nerves to the visceral surfaces are supplied by the vagus, 
glossopharyngeal and facial nerves. 
In van Wijhe’s original paper he arranged the segments belonging 
to the cranial nerves in the following table :— 
Segments. ig pe ee ole aaa Visceral clefts. Dorsal nerve-roots and muscles. 
1 III. M. rectus supe- V. N. op- 
rior, m. rectus thalmicus 
internus, m. profundus 
rectus inferior, 
m. obliquus in- 
ferior 
2 IV. M. obliquus V. Masticating 
superior 1st Mandibular muscles. 
3 VI. M. rectus ex- VIL. {vit aria 
ternus - 1 
Hyoid branch of VII.) 
4 = ee and{ aye Ay VIL., 
5 _— — 8rd 1st Branchial IX. | 
6 = = 4th Ind, X. . 
7 XII. |] Muscles from (5th 8rd See 
8 XII. cranium to 6th 4th 5 X.,; | ‘ 
9. XII. | shoulder-girdle 7th 5th 5 X., | 
‘ 
As is seen in the table, van Wijhe attempts to arrange the cranial 
segmental nerves into dorsal and ventral roots, in accordance with 
the arrangement in the spinal region. In order to do this he calls 
the Vth, VIIth, IXth, and Xth nerves dorsal roots, although they 
are not purely sensory nerves, but contain motor fibres as well. 
It is not accidental that he should have picked out for his dorsal 
roots the very nerves which form Charles Bell’s lateral series of 
roots, inasmuch as this system of lateral roots, apart from dorsal and 
ventral roots, really is, as Charles Bell thought, an important separate 
system, dependent upon a separate segmentation in the embryo of 
the musculature supplied by these roots. This segmentation may 
receive the name of visceral or splanchnic in contradistinction to 
somatic, since all the muscles without exception belong to the visceral 
group of striated muscles. 
