336 THE SPINAL NERVES. 



sometimes arise together, and the upper one occasionally springs from the great 

 sciatic nerve before the bifurcation. From the lower branch a filament is given to 

 the superior tibio-fibular articulation (Eiidinger). 



From the place of division of the external popliteal nerve, a branch (often double) 

 called the recurrent articular nerve ascends through the tibialis anticus with the 

 anterior tibial recurrent artery ; its fibres terminate mainly in that muscle, but fila- 

 ments may be traced to the superior tibio-fibular articulation, the periosteum over 

 the outer tuberosity of the tibia, and the fore part of the knee-joint. 



(b) The cutaneous branches (5 /, 1, 2 s), generally two in number, supply the skin 

 on the back part and outer side of the leg. 



The peroneal or fibular communicatiny branch, which usually joins the short 

 saphenous nerve below the middle of the back of the leg, is the largest of these 

 nerves. In some instances, it continues as a separate branch, and its cutaneous 

 filaments reach down to the heel or on to the outer side of the foot. 



The lateral cutaneous branch of the leg (n. cutaneus sune laterals), often 

 arising in conjunction with the foregoing, extends along the outer side of the leg 

 to the middle or lower part, sending offsets both backwards and forwards. 



In some cases there is another cutaneous branch which arises from the upper part of the 

 external popliteal nerve, and ramifies over the back of the calf, taking the place of the small 

 sciatic nerve below the knee. 



Musculo -cutaneous nerve. The musculo-cutaneous nerve (n.peronceussuper- 

 ficialis) (4, 5 /, Is) descends between the peronei muscles and the long extensor of 

 the toes, and reaches the surface by perforating the fascia in the lower part of the 

 leg on the anterior aspect. It then divides into two branches, distinguished as 

 external and internal, which proceed to the toes. The two branches sometimes 

 perforate the fascia at different spots. 



Branches. (a) Muscular branches are given to the peroneus longus and peroneus 

 brevis. 



(b) Cutaneous branches given off near the primary division are distributed to the 

 lower part of the leg. 



(c) The internal branch of , the musculo-cutaneous nerve, passing forwards along 

 the dorsum of the foot, furnishes one branch to the inner side of the great toe, and 

 another to the contiguous sides of the second and third toes. It also gives offsets 

 which extend over the inner ankle and side of the foot. This nerve communicates 

 with the long saphenous nerve on the inner side of the foot, and with the anterior 

 tibial nerve between the first and second toes. 



(d) The external branch, smaller than the internal, descends over the foot 

 towards the fourth toe, tvhich, together with the contiguous borders of the third 

 and fifth toes, it supplies with branches. Cutaneous nerves, derived from this 

 branch, spread over the outer ankle and the outer side of the foot, where they are 

 connected with the short saphenous nerve. 



The dorsal digital nerves are continued on to the last phalanges of the toes. 



The number of toes supplied by each of the two divisions of the musculo- 

 cutaneous nerve is liable to vary ; together, these nerves commonly supply all the 

 toes. on the dorsal aspect, excepting the outer side of the little toe, which receives a 

 branch from the short saphenous nerve, and the adjacent sides of the great toe and 

 the second toe, to which the anterior tibial nerve is distributed : with this latter 

 branch, however, it generally communicates. 



Varieties. The external division of the musculo-cutaneous nerve is often reduced in size, 

 the deficiency being supplied by the external saphenous nerve. Less frequently the internal 

 branch is replaced to a greater or lets extent en the toes by the anterior tibial nerve. The 



