'/'///: TI/l/AL M-h'VH 949 



side of the vein ami arten : at the middle of the space it is behind and in the lower 

 part of the .space it is internal to both of them. 



The branches given oil' by the tibial nerve in the popliteal space are articular, 

 cutaneous, and muscular. 



The articular branches are usually three in number, a superior and an inferior 

 internal articular and an azygos articular. They accompany the- corresponding ar- 

 teries, and, after piercing the ligaments, are distributed in the interior of the joint. 

 The superior branch is often want ini. 



The cutaneous branch, the medial sural cutaneous (tibial communicating) nerve, 

 descends between the heads of the gastrocnemius, beneath the deep fascia, to the 

 middle of the calf, where it pierces t he fascia and unites with the peroneal anastomotic 

 branch of the lateral sural cutaneous to form the sural (external saphenous) nerve, 

 through which its fibres are distributed to the skin of the lower and back part of the 

 les; and the outer side of the foot. 



The muscular branches are distributed to both heads of the gastrocnemius, to 

 the plantaris, soleus, and popliteus. The nerve to the soleus is relatively large, and 

 passes between the outer head of the gastrocnemius and the plantaris before it 

 reaches its termination (fig. 695). The nerve to the popliteus descends on the pos- 

 terior surface of the muscle, turns around its lower border, and is distributed on its 

 anterior aspect. In addition to supplying the popliteus, it gives articular branches 

 to the knee and superior tibio-fibular joints, a branch to the tibia which accompanies 

 the medullary artery, and a long, slender twig which gives filaments to the anterior 

 and posterior tibial arteries, and it descends as the interosseous crural nerve (Hal- 

 bertsma) on the interosseous membrane to the inferior tibio-fibular joint. It also 

 gives branches to the interosseous membrane and to the periosteum of the lower 

 part of the tibia. 



In the upper part of the leg the tibial nerve is placed deeply, under cover of the 

 gastrocnemius and soleus, but in the lower half it is merely covered by the deep 

 fascia, which is thickened between the internal malleolus and the calcaneus to form 

 the laciniate (internal annular) ligament, and the termination of the nerve lies either 

 under cover of this ligament, or under the origin of the abductor hallucis. The an- 

 terior relations of the nerve are, from above downwards, the tibialis posterior, the 

 flexor digitorum longus, the lower part of the tibia, and the posterior ligament 

 of the ankle-joint. For a short distance after its commencement the nerve lies to the 

 inner side of the posterior tibial artery; then it crosses behind the artery and runs 

 downwards along its outer side. 



The branches of the lower part of the tibial nerve (below the popliteal space) 

 are likewise muscular, cutaneous, and articular. They are supplied to the deep 

 muscles of the back of the leg, to the fibula, to the skin of the heel and foot, and to 

 the ankle-joint. Several of the terminal branches are important enough to receive 

 special names and special treatment. 



The muscular branches pass from the upper part of the nerve to the tibialis 

 posterior, flexor digitorum longus, soleus, and flexor hallucis longus. The ribular 

 branch arises with the nerve to the flexor hallucis longus, and accompanies the per- 

 oneal artery. It supplies the periosteum and gives filaments which accompany the 

 medullary artery. 



The articular branches arise from the lower part of the nerve, immediately above 

 its terminal branches, and they pass into the joint through the internal lateral 

 ligament. 



The medial calcaneal (calcaneo-plantar cutaneous) nerves arise from the 

 trunk of the tibial nerve in the lower part of the leg. They pierce the laciniate 

 (internal annular) ligament, and are distributed to the integument of the inner side 

 and under surface of the heel and the adjoining part of the sole of the foot (fig. 695). 



The medial plantar nerve is the larger of the two terminal branches of the 

 tibial nerve. It commences under cover of the lower border of the laciniate (internal 

 annular) ligament, or under the posterior border of the abductor hallucis, and 

 passes forwards, accompanied by the small internal plantar artery, in the inter- 

 muscular septum between the abductor hallucis and the flexor digitorum brevis. 

 At the middle of the length of the foot it becomes superficial, in the interval be- 

 tween the two muscles, and divides into four sets of terminal branches (fig. 696): 



(a) Branches. Muscular branches pass from the trunk of the nerve to the ab- 

 ductor hallucis and the flexor digitorum brevis. 



