THE NERVOUS SYSTEM 157 



gical position of this nerve advanced by these and other authors 

 are given below. 



The brachial plexus was well described by Fiirbringer in 1873, 

 and his account was republished five years later by Hoffmann in 

 Bronn's Thier-reich. In this latter work Hoffmann also published 

 an account, accompanied by an original figure of the crural plexus. 

 His description is not quite complete. 



A number of authors have dealt with various details connected 

 with the nerves of the limbs in papers primarily concerned with 

 muscles, which are summarized in the muscle-section of the 

 present work. Amongst these may be mentioned Sieglbaur, Rib- 

 bing, Appleton, and McMurrich. 



Amongst the synonyms given will be found the names of authors 

 dealing with Urodeles other than Salamandra, which have been 

 included to facilitate comparison. 



The method adopted here is the same as that chosen by Gaupp in 

 his Anatomie des Frosches^ v'yl. to describe first a typical spinal nerve 

 — for which purpose N. spinalis 10 has been chosen — and then to 

 give an account of the ventral rami of those nerves which become 

 specially modified, e.g. N. hypoglossus, and the nerves supplying 

 the fore- and hind-limbs. 



2. A Typical Spinal Nerve. 



iV. spinalis 10 (PI. XXIV, fig. 79) arises from the spinal cord by 

 a dorsal and a ventral root. The dorsal root arises some distance 

 posterior to the ventral root, but both pass together through a special 

 foramen in the neural arch immediately posterior to the transverse 

 process of the ninth vertebra (see also p. 19). The two roots 

 fuse within the foramen, and immediately after emerging from it 

 swell into a large ganglion — the spinal ganglion 10 (g.sp.io). The 

 spinal ganglion thus lies outside the vertebral column, but it is never- 

 theless protected by the transverse process anteriorly, and by the 

 broad articular processes dorsally, as well as by the tough fibrous sac 

 in which it is enclosed. Within this sac, surrounding the ganglion, 

 is a spongy fatty tissue, and there is no trace of the chalky masses 

 found in this position in the frog. 



From the ganglion emerge the usual dorsal and ventral rami, each 

 being composed of motor and sensory fibres, and supplying respec- 

 tively the dorsal and ventral body muscles and the skin overlying them. 



R. dorsalis. This ramus arises from the ganglion as several 

 twigs. The largest of these emerges dorsally, then turning directly 

 caudad, passes alongside the vertebral column almost to the level 



