i66 THE SALAMANDER 



branch which supplies the MM. ext. brev. dig. I, and abductor 

 digiti I. 



{b) The second branch is the N. dorsalis manus ulnaris (n.d.m.u.). 

 Almost immediately after its separation it receives one of the 

 terminal branches of the N. extensorius caudalis (q.v.). It then runs 

 along the fore-arm over the ulna, parallel with the previous branch, 

 and gives off one or two twigs which pass outwards, between the 

 MM. extensores antibr. et carpi radialis and ulnaris, to supply the 

 M. extensor digitorum communis. From these twigs fibres may 

 also pass into the M. extensor antibr. et carpi radialis. In the region 

 of the wrist this nerve becomes more superficial and lies directly under 

 the M. extensor digitorum communis, and, after giving off a branch 

 to supply the skin on the ulnar side of the fourth digit, it crosses to 

 the space between the third and fourth digits and divides to supply 

 the skin on the adjoining sides of these two fingers. It also gives fine 

 twigs to the MM. extensores breves digitorum III and IV. 



N. extensorius caudalis (n.ex.cd.). Sieglbaur (1904). 

 Posterior ulnar, or better, inferior 



musculo-spiral nerve . ..... Humphry (1871). 



N. radialis superficialis . . Fiirbringer (1873); Hoffmann (1873-8)^ 



Ribbing (1907). 

 N. radialis inferior ...... Osawa (1902). 



This is the smaller of the two extensor nerves and is separated 

 from the anterior extensor nerve by the Vena brachialis medialis, but 

 receives one or two fine anastomosing twigs from it. It arises more 

 definitely from the N. spinalis 3-4 anastomosis than does the N. ex- 

 tensorius cranialis. 



Soon after entering the arm it gives off a large cutaneous branch, 

 N. cutaneus brachii dorsalis (n.cut.br.d.). This branch often carries 

 some motor-fibres for the MM. anconaeus scapularis medialis and 

 anconaeus coracoideus. Then follows a short branch which divides 

 into three and supplies the scapularis medialis, humeralis and cora- 

 coideus portions of the anconaeus muscle, while a little farther on a 

 small twig is given off to the M. anconaeus humeralis lateralis. Still 

 farther distalwards another twig to the M. anconaeus coracoideus 

 may frequently be found. 



On reaching the flexor side of the elbow the nerve bends round 

 the antero-lateral edge of the M. anc. hum. lat., and passes to the 

 extensor side of the fore-arm, crossing obliquely over the origin of 

 the M. extensor digit, comm., between the muscle and the skin. At 

 the elbow it gives a cutaneous branch to the ulnar side of the fore- 



