THE FIBULAR REGION. 441 



It terminates in a long tendon, which passes behind the outer malleolus, in a 

 groove common to it and the tendon of the Peroneus brevis, behind which it lies, 

 the groove being converted into a canal by a fibrous band, and the tendons 

 invested by a common synovia! membrane ; it is then reflected obliquely forward 

 across the outer side of the os calcis, below its peroneal tubercle, being contained 

 in a separate fibrous sheath, lined by a prolongation of the synovial membrane 

 which lines the groove behind the malleolus. Having reached the outer side of 

 the cuboid bone, it runs in a groove on the under surface of that bone, which is 

 converted into a canal by the long calcaneo-cuboid ligament, and is lined by a 

 synovial membrane : the tendon then crosses the sole of the foot obliquely, 

 and is inserted into the outer side of the base of the metatarsal bone of the 

 great toe and the internal cuneiform bone. Occasionally it sends a slip to> 

 the base of the second metatarsal bone. The tendon changes its direction at 

 two points : first, behind the external malleolus ; secondly, on the outer side 

 of the cuboid bone ; in both of these situations the tendon is thickened, and 

 in the latter a sesamoid fibro-cartilage, or sometimes a bone, is usually developed 

 in its substance. 



Relations. By its superficial surface, with the fascia and integument ; by its 

 deep surface, with the fibula, external popliteal nerve, the Peroneus brevis, os 

 calcis, and cuboid bone; by its anterior border, with an intermuscular septum, 

 which intervenes between it and the Extensor longus digitorum ; by its posterior 

 border, with an intermuscular septum, which separates it from the Soleus above 

 and the Flexor longus hallucis below. 



The Peroneus brevis lies beneath the Peroneus longus, and is shorter and 

 smaller than it. It arises from the lower two-thirds of the external surface of 

 the shaft of the fibula, internal to the Peroneus longus, and from the intermuscular 

 septa separating it from the adjacent muscles on the front and back part of the 

 leg. The fibres pass vertically downward, and terminate in a tendon which runs 

 in front of that of the preceding muscle through the same groove, behind the 

 external malleolus, being contained in the same fibrous sheath and lubricated by 

 the same synovial membrane. It then passes through a separate sheath on the 

 outer side of the os calcis, above that for the tendon of the Peroneus longrus, the 



7 O / 



two tendons being here separated by the peroneal tubercle, and is finally inserted 

 into the tuberosity at the base of the metatarsal bone of the little toe, on its 

 outer side. 



Relations. By its superficial surface, with the Peroneus longus and the fascia 

 of the leg and foot ; by its deep surface, with the fibula and outer side of the 

 os calcis. 



Nerves. The Peroneus longus and brevis are supplied by the fourth and fifth 

 lumbar and first sacral nerves through the musculo-cutaneous branch of the 

 external popliteal nerve. 



Actions. The Peroneus longus and brevis extend the foot upon the leg, in 

 conjunction with the Tibialis posticus, antagonizing the Tibialis anticus and 

 Peroneus tertius, which are flexors of the foot. The Peroneus longus also everts 

 the sole of the foot ; hence the extreme eversion occasionally observed in fracture 

 of the lower end of the fibula, where that bone offers no resistance to the action 

 of this muscle. From the oblique direction of the Peroneus longus tendon across 

 the sole of the foot it is an important agent in the maintenance of the transverse 

 arch of the foot. Taking their fixed point below, the Peronei serve to steady the 

 leg upon the foot. This is especially the case in standing upon one leg, when 

 the tendency of the superincumbent weight is to throw the leg inward : the 

 Peroneus longus overcomes this tendency by drawing on the outer side of the 

 leg, and thus maintains the perpendicular direction of the limb. 



Surgical Anatomy. The student should now consider the position of the tendons of the 

 various muscles of the leg, their relation with the ankle-joint and surrounding blood-vessels, and 

 especially their action upon the foot, as their rigidity and contraction give rise to one or other of 

 the kinds of deformity known as dub-foot. The most simple and common deformity, and one 



