lyo THE SALAMANDER 



nerve becomes more superficial again at the wrist, where it passes 

 dorsal to the tendon of insertion of the M. cap. long. muse, contra., 

 between the basalia of digits i and 3. At the interspace of these 

 digits it bifurcates and each ramus again divides into two, so that 

 the posterior ramus supplies the skin on the pre-axial side of the 

 third digit — N. digitalis ventralis 3 — and also joins the terminal twig 

 of the N. ulnaris, while the anterior ramus similarly innervates the 

 post-axial side of the second finger — N. dig. vent. 2 — and then passes 

 across to the interspace of the first and second digits and sup- 

 plies the skin of their adjoining sides — NN. dig. vent, i and 2 — and 

 finally joins the N. cut. inf. lat. It is not certain that this latter fusion 

 is quite constant, but it certainly occurs in a sufficient number of 

 cases to justify its being considered 'normal'. There is thus a com- 

 plete nerve loop across the palm. The N. interosseus also innervates 

 the short flexor muscles of digits 2 and 3 by small twigs in the appro- 

 priate places. 



The ventral ramus of the Jifik spinal nerve (n.sp.5), on emerging 

 from the subvertebral muscles, divides into two branches, and the 

 posterior one divides again several times to supply the various 

 muscles of the ventral body-wall in that region. The anterior branch 

 also divides again, one branch anastomosing with N. spinalis 4 and 

 entering the brachial plexus, while the other is distributed to the 

 skin of the axilla and the ventro-posterior side of the arm. This 

 branch is usually joined by a branch arising direct from the plexus 

 3-4 which is somewhat variable in size, and in one case could not 

 be found. The resulting nerve may be called N. cutaneus brachii 

 ventralis (n.cut.br.v.). 



Fiirbringer seems to have overlooked this nerve unless it is repre- 

 sented by one of the 'Aeste fur Bauchmuskeln' which he has not 

 followed in detail. This author also figures a condition sometimes 

 met with, in which the branch entering N. spinalis 4 bifurcates just 

 before doing so, and sends a small twig to join the N. pectoralis. 

 From this, and from the fact that the fifth nerve nearly always enters 

 the fourth close to the point whence the N. pectoralis emerges, it 

 seems safe to conclude that at least some fibres from the fifth spinal 

 nerve normally contribute to the pectoral nerve. 



6. Crural Plexus, and Nerves of the Hind-limb (PI. XII). 



The crural plexus of the Salamander is formed by the fifteenth, 

 sixteenth, and seventeenth spinal nerves, with small contributions from 

 the fourteenth and eighteenth. The main nerves of the plexus are 



