270 MUSCLES OF THE FOOT. 



neath 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 o'f the os calcis. 



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

 with the tibialis posticus. They antagonise the tibialis anticus and 

 peroneus 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. 



FOOT. 



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. 



Relations. By its upper surface with the tendons of the extensor 

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

 By its under 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. 



The DORSAL INTEROSSEI muscles are placed between the metatarsal 

 bones; they resemble the analogous muscles in the hand in arising 

 by two heads from the adjacent sides of the metatarsal bones ; their 

 tendons are inserted into the base of the first phalanx, and into the 

 digital expansion of the tendons of the long extensor. 



The first dorsal interosseous is inserted into the inner side of the 

 second toe, and is therefore an adductor; the other three are inserted 

 into the outer side of the second, third, and fourth toes, and are conse- 

 quently abductors. 



Relations. By their upper surface with a strong fascia which sepa- 

 rates them from the extensor tendons. By their under surface with 

 the plantar interossei. Each of the muscles gives passage to a small 

 artery (posterior perforating) which communicates with the external 

 plantar artery. And between the heads of the first interosseous 

 muscle the communicating artery of the dorsalis pedis takes its course. 



