156 ANATOMY IN A NUTSHELL. 



Origin.— (Plate L.) — (1) Lower two-thirds of posterior surface of shaft 

 of fibula except an inch at lowest part: (2) lower part of interosseous mem- 

 brane; (3) intermuscular septum; (4) fascia covering Tibialis posticus. 



Insertion. — (Plate LIII.) Base of last phalanx of great toe. 



Action. Flexes ureal toe and extends foot. 



Nerve Supply. Fifth lumbar and first and second sacral through pos- 

 terior tibial. 



Blood Supply. — Posterior tibial. 



Flexor Longus digitorum.— Description. — (Plate LXXIX.) — This muscle 

 is small at its origin but gradually increases in size as it descends. Its tendon 

 occupies nearly all of the posterior surface of the muscle. The tendons of the 

 Tibialis posticus and this muscle pass through a common groove behind the 

 internal malleolus, but each tendon has its own synovial sheath. They are 

 separated from each other by a fibrous septum. As the tendon crosses the sole 

 of the foot obliquely forward and outward, it divides into four tendons each of 

 which passes through the tendons of the Flexor brevis digitorum opposite the 

 base of the first phalanx. Just before it divides it is joined by the Flexor ac- 

 cessories. 



Origin.- -(Piatt 1 L.) — Posterior surface of shaft of tibia, immediately below 

 i lie oblique line to within three inches of its extremity internal to the tibial 

 origin of the Tibialis posticus. 



Insertion. — (Plate LIII.) — Into bases of last phalanges of the four lesser 

 toes. 



A.CTION. — Flexes toes and extends foot. 



Nerve Supply. — Fifth lumbar and first sacral through posterior tibial. 



Blood Supply. — Posterior tibial. 



Tibialis posticus. — Description. — (Plate LXXIX.) — This muscle is the 

 mosl deeply seated of all the muscles of the leg. and it lies between the Flexor 

 Longus hallucis and the flexor longus digitorum. Between its two heads pass 

 the anterior tibial vessels to the front of the leg. Its tendon passes through a 

 groove behind the internal malleolus in its own sheath. It then passes through 

 another sheath over the internal lateral ligament into the foot and then beneath 

 the inferior calcaneonavicular ligament to its insertion. It sends fibers of in- 

 sertion to all the bones of the tarsus except the astragalus, also to second, third, 

 and fourth metatarsal bones. 



( >rigin. ( Plate L.) — Whole of posterior surface of interosseous membrane, 

 excepting lowesl part; from outer portion of posterior surface of shaft of tibia, 

 between commencement of oblique line above and junction of middle and lower 

 third of shaft below; from upper two-thirds of the internal surface of fibula; 

 some fibers a bo from deep transverse fascia and intermuscular septa. 



I nsertion. (Plate bill.) —Tuberosity of navicular and internal cuneiform 

 bono and bases of second, third, ami fourth metatarsal. 



Action. Extends tarsus; turns sole inward. 



Nerve Supply.— Fifth lumbar and first sacral through posterior tibial. 



Blood Si pply. Posterior tibial. 



Peroneus longus.- Description. — (Plate LXXIX.) — The Peroneus Ion- 



