656 



HUMAN ANATOMY. 



Relations. — By its deep surface and m 

 the extensor longus hallucis, medially with the 



Fig. 623. 



Head 

 of fibula 



Tubercle of tibia 



Peroneus 

 longus 



Portion of deep 

 fascia of leg 



alf muscles 

 Tibia 



■Tibialis anticus 



Intermuscular 

 septum attached 

 to fibula 



Peroneus brevis. 



Fibula 



Peroneus brevis 

 tendon 



Outer malleolus 



Extensor 

 brevis digitorum 



Peroneus tertius 

 tendon 



Base of fifth 

 metatarsus 



Extensor longus 

 digitorum 



Extensor 

 longus hallucis 



Peroneus tertius 



Inner malleolus 



Anterior annu- 

 lar ligament, 

 vertical por- 

 tion 



Anterior an- 

 nular ligament, 

 horizontal por- 

 tion 



Extensor brevis 

 digitorum 



Superficial dissection of anterior surface of right leg, 

 showing muscles undisturbed. 



edially the muscle is in relation with 

 tibialis anticus, the anterior tibial ves- 

 sels and nerve, and deeply with the 

 deep peroneal nerve above and the 

 ankle-joint below. Laterally it is in 

 contact with the peroneus longus 

 above, with the peroneus tertius be- 

 low, and with the musculo-cutaneous 

 nerve, which passes downward be- 

 tween it and the peroneus longus 

 (Fig. 617). 



Variations . — Considerable variation 

 occurs in the arrangement of the terminal 

 tendons, one of the most usual departures 

 from the typical condition being a duplica- 

 tion of the tendon to one or more of the 

 toes, the additional tendon either passing 

 to the same digit as its fellow or to an 

 adjacent one. Occasionally a slip passes 

 from the innermost tendon to that of the 

 extensor longus hallucis, and slips may 

 pass from any of the tendons to the meta- 

 tarsal bones. 



3. Peroneus Tertius (Fig. 623). 



Attachments. — The peroneus 

 tertius arises from the lower part of 

 the anterior surface of the fibula and 

 from the interosseous membrane, the 

 intermuscular septum, and the crural 

 fascia. At about the level of the 

 ankle its fibres pass over into a ten- 

 don which continues through the 

 lateral compartment of the anterior 

 annular ligament, together with the 

 tendon of the extensor longus digi- 

 torum, and is inserted into the base 

 of the fifth metatarsal bone. 



Nerve-Supply. — By the ante- 

 rior tibial nerve from the fourth and 

 fifth lumbar and first sacral nerves. 



Action. — To flex and evert the 

 foot. 



Variations. — The peroneus tertius is 

 quite frequently absent, and is usually more 

 or less closely united with the extensor 

 longus digitorum above. Its tendon some- 

 times splits into two portions, the additional 

 one passing either to the fifth toe or to the 

 fourth metatarsal. 



Notwithstanding its name, which has 

 reference to its origin from the fibula, 

 the peroneus tertius has morphologically 

 nothing to do with the other peroneal 

 muscles, but is a separated portion of the 

 extensor longus digitorum, whose connec- 

 tions with the metatarsals are interesting 

 in this regard. 



4. Extensor Longus Hallucis (Fig. 624). 

 Attachments. — The long or proper extensor of the great toe (tn. extensor hallucis 

 longus) arises from the inner surface of the fibula and from the interosseous membrane. 



