MUSCLES OF THE FOOT. 241 



has but two tendinous sheaths arid 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, con- 

 jointly with the tibialis posticus. They antagonise the tibralis 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 con- 

 sequently abductors. 



Relations. By their upper surface with a strong fascia which 

 separates 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 interos- 

 seous muscle the communicating artery of the dorsalis pedis takes 

 its course. 



Plantar Region. 

 First Layer. 



Abductor pollicis, 

 Abductor minimi digiti, 

 Flexor brevis digitorum. 

 31 



A 



