178 THE SALAMANDER 



It passes down the fibular side of the leg deep to the M. flexor 

 primordialis communis, between this muscle and the M. flexor 

 accessorius medialis. Directly after separating from the N. interos- 

 seus the fibular nerve gives off a R. medianus (n.f.m.), which passes 

 along the mesial — pre-axial — side of the M. cap. long. muse, contra. 

 It innervates this muscle (c.l.c), as well as M. flex. ace. lat. (f.a.L), 

 and terminates finally in the M. flex. ace. med. (f.a.m.). Just after 

 it separates from the N. fibularis it gives a small twig to the M. plant, 

 super, minor (pi.") of Eisler. 



The main N. fibularis lies post-axial to the M. cap. long. muse, 

 contra., close to the fibula. It may send a twig to the M. cap. long, 

 muse, contra, (c.l.c), but its main function is to innervate the M. 

 flex. prim. comm. (f.p.c), and the short flexor muscles of the fifth 

 digit (a.d.5 and e.b.5). It also gives a cutaneous branch to the post- 

 axial side of the fifth toe, N. digit, vent. 5. An anastomosis between 

 a terminal branch of this nerve and one from the posterior ramus of 

 the N. interosseus is usually demonstrable. 



A^. interosseus (n.io.) (mihi). 



Internal popliteal . ...... Humphry (187 1). 



R. medialis n. ischiadici . .... Hoffmann (1873-8). 



N. tibialis medianus ...... Sieglbaur (1904). 



This branch passes down the leg in the interosseal space between 

 the tibia and fibula dorsal to the M. interosseus cruris. It supplies 

 this muscle (i.e.), as well as the M. pronator profundus (p.p.)- I^ 

 appears again from beneath the muscle at the tarsus, between the 

 tarsal bones of the second and third digits, but remains dorsal to the 

 tendinous insertion of the M. cap. long. muse, contra. In this region 

 it divides into three. One branch passes directly to the interdigital 

 space of the second and third toes, where it bifurcates into the 

 NN. digit, vent. 2 and 3, and the other two branches (which would 

 seem to correspond to Humphry's anterior and posterior tibial 

 nerves) similarly form the NN. digit, vent, i and 2, 3 and 4, and also 

 4 and 5, and in addition give twigs to all the short flexor muscles of 

 these digits. The post-axial branch usually joins a terminal branch 

 from the fibular nerve, while the pre-axial twig may — but probably 

 does not always — anastomose with one from the N. cut. fem. ventr. 



It should be noted that, in the Salamander, there is no exchange of 

 fibres between this nerve and the dorsal, or extensor, nerves as there 

 is in many Urodeles. 



The ventral ramus of N. spinalis 18 bifurcates, immediately after 

 penetrating the ilio-caudalis muscle, and the anterior portion passes 



