258 FOOT DORSAL REGION. 



Dissection. These muscles are exposed by continuing the dissection 

 of the anterior tibial region outwards beyond the fibula, to the border of 

 the posterior tibial region. 



The PERONEUS LONGUS (ITSPOVIJ, fibula, extensor tarsi fibularis longioi) 

 muscle arises from the head and upper third of the outer side of the fibula, 

 and terminates in a long tendon, which passes behind the external mal- 

 leolus, and obliquely across the sole of the foot, through the groove in the 

 cuboid bone, to be inserted into the base of the metatarsal bone of the 

 great toe. Its tendon is thickened where it glides behind the external 

 malleolus, and a sesamoid bone is developed in that part which plays 

 upon the cuboid bone. 



Relations. By its superficial surface with the fascia of the leg and foot. 

 By its deep surface with the fibula, peroneus brevis, os calcis, and cuboid 

 bone, and near the head of the fibula with the fibular nerve. By its ante- 

 rior border it is separated from the extensor longus digitorum by the 

 attachment of the fascia of the leg to the fibula ; and by the posterior 

 border by the same medium from the soleus and flexor longus pollicis. 

 The peroneus longus is furnished with three tendinous sheaths and as 

 many synovial membranes ; the first is situated behind the external mal- 

 leolus, and is common to this muscle and the peroneous brevis, the second 

 on the outer side of the os calcis, and the third on the cuboid bone. 



The PERONEUS BREVIS (extensor tarsi fibularis brevior) lies beneath the 

 peroneus longus; it arises from the lower half of the fibula, and terminates 

 in a tendon which passes behind the external malleolus and through a 

 groove in the os calcis, to be inserted into the base of the metatarsal bone 

 of the little toe. 



Relations. By its superficial surface with the peroneus longus and 

 fascia of the leg and foot. By its deep surface with the fibula, the os 

 calcis, and cuboid bone. The lateral relations are the same as those of 

 the peroneus longus. The tendon of the peroneus brevis has but two 

 tendinous sheaths and two synovial membranes, one behind the external 

 malleolus and common to both peronei, the other upon the side of the os 

 calcis. 



Actions. The peronei muscles are extensors of the foot, conjointly 

 with the tibialis posticus. They antagonize the tibialis anticus and pero- 

 neus tertius, which are flexors of the foot. The whole of these muscles 

 acting together, tend to maintain the flatness of the foot, so necessary to 

 security in walking. 



FO o T. 



Dorsal Region. 

 Extensor brevis digitorum, Interossei dorsales. 



The EXTENSOR BREVIS DIGITORUM muscle arises from the outer side of 

 the os calcis, crosses the foot obliquely, and terminates in four tendons, 

 the innermost of which is inserted into the base of the first phalanx of the 

 great toe, and the other three into the sides of the long extensor tendons 

 of the second, third, and fourth toes. 



Rtlutions. By its upper surface with the tendons of the extensor longus 

 digitorum, peroneus brevis, and with the deep fascia of the foot. By its 

 wider surface with the tarsal and metatarsal bones. Its inner border is in 

 relation with the dorsalis pedis artery, and the innermost tendon of the 

 muscle crosses that artery just before its division. 



