THE MUSCLES OF THE LEG AND FOOT. 



425 



M. Extensor Digitorum Longus. The extensor digitorum longus arises, by 

 fleshy fibres, from the lateral side of the lateral condyle of the tibia, from the 

 proximal two-thirds or more of the anterior part of the medial surface of the body 

 of the fibula, from the fascia over it, and from intermuscular septa on either side. 



It gives rise to a tendon which passes deep to the ligamentum transversum 

 and cruciatum, and in front of the ankle subdivides into four tendons, inserted 

 into the four lateral toes, exactly in the same way as the corresponding tendons 

 in the hand (see p. 397). They form membranous expansions on the dorsum of the 

 first phalanx, joined by the tendons of the extensor digitorum brevis, lumbricales, 



Abductor digiti quinti 

 (origin) 



Quadratus plantse (origin) 



Long plantar ligament 



Plantar calcaneo-cuboid 

 ligament 



Tibialis posterior (part of 

 insertion) 



Peronseus brevis 

 (insertion) 



Flexor digiti quinti 

 brevis (origin) 



Adductor hallucis 



(origin of oblique 



head) 



Flexor digitorum brevis (origin) 

 Abductor hallucis (origin) 



Attachments of 

 plantar calcaneo- 

 navicular ligament 



Flexor hallucis brevis 

 (origin) 



Tibialis posterior 

 (main part of insertion) 



Peronseus longus 

 (insertion) 



Tibialis anterior 

 (insertion) 



FIG. 379. MUSCLE- ATTACHMENTS TO LEFT TARSUS AND METATARSUS (Plantar Aspect). 



and interossei, each of which separates into one central and two collateral slips, 

 attached respectively to the middle and terminal phalanges. The tendon occupies 

 a separate compartment, along with the peronaeus tertius, deep to the ligamentum 

 cruciatum cruris, invested by a special mucous sheath. 



Nerve-Supply. Deep peroneal nerve (L. 4. 5. S. 1.). 



Actions. A dorsi-flexor of the ankle and an extensor of the four lateral toes. 



M. Peronseus Tertius. The peronseus tertius is a separated portion of the 

 extensor digitorum longus. It is an essentially human muscle. It arises (insepar- 

 ably from the extensor digitorum longus) from the anterior part of the medial 

 surface of the fibula, and from the inter-muscular septum lateral to it. 



