THE NERVOUS SYSTEM 159 



The second spinal nerve is normal with regard to its dorsal root, 

 ganglion, and cutaneous branches, but its ventral ramus contributes 

 both to the N. hypoglossus — supplying the tongue muscles — and to 

 the brachial plexus. 



The third, fourth, and fifth spinal nerves are all exceptional in that 

 their ventral rami enter into the brachial plexus and supply the 

 muscles of the fore-limb and shoulder. 



The ventral rami of the fifteenth, sixteenth, and seventeenth 

 spinal nerves similarly anastomose to form the crural plexus supply- 

 ing the muscles of the pelvis and hind-limb. To this plexus the 

 fourteenth and eighteenth spinal nerves also contribute, but only in 

 a minor degree. 



3. The First Spinal Nerve. 



TV", spinalis 1 (= N. spinalis 2, Hoffmann) (PI. X, fig. 54, n.sp.i). 

 There has been some controversy over the morphological position 

 of this nerve, together with the related question of the segmentation 

 of the occipital region of the skull and of the 'atlas' vertebra (see also 



P- 17)- 



So far as it is possible to separate the discussions concerning the 

 nerve itself from those relating to the skeletal structures they may 

 be briefly stated as follows. 



In 1878 Hoffmann suggested that the first vertebra of Urodeles 

 actually represents two vertebrae fused because it is penetrated by 

 the first spinal nerve. In 1902 he confirmed this view by studying 

 the larval stages of Triton and Salamandra. He then found the 

 ventral root of a transitory nerve emerging between the occipital 

 condyles and the vertebral column — N. suboccipitalis — and related 

 to the first myotome. He regarded this transitory nerve as the first 

 spinal nerve because it emerges between the occiput and the verte- 

 bral column, and therefore he argued that the first spinal nerve of 

 the adult is morphologically N. spinalis 2. He also found an even 

 more transitory nerve (ventral root only) anterior to the N. sub- 

 occipitalis belonging to his myotome-o. 



Druner (1904) disagreed with this view. He accepted Peter's 

 explanation that the atlas vertebra was single and not two vertebrae 

 fused, and said (Teil II, p. 439, footnote): *Nach meinen Befunden 

 ist der den i . Wirbel durchsetzende Nerv mit demjenigen identisch, 

 welchen C. K. Hoffmann bei jiingern Embryonen zwischen Occipi- 

 talknorpel und i. Wirbelbogen austreten sah.' 



Goodrich (191 1) apparently arrived at similar results from the 

 study of the larva of Amblystoma. 



