364 TEE MUSCLES. 



the tendon of the peroneus, and a funicular prolongation of the tibial aponeurosis. 

 It afterwards descends on the fetlock, where it comports itself exactly as the 

 corresponding tendon in the anterior extremity (see the extensor pedis in the 

 fore limb, p. 324). 



Attachments. — Above, in the digital fossa between the trochlea and external 

 condyle of the femur, through the medium of the tendinous portion of the flexor 

 metatarsi— ^j-et? insertion. Below, on the capsular ligament of the metatarso- 

 phalangeal articulation, the anterior face of the two first phalanges, and the 

 pyramidal process of the os pedis. 



Relations. — The muscular portion responds : outwardly, with the tibial 

 aponeurosis ; inwardly, to the flexor metatarsi ; posteriorly, to the peroneus. 

 The tendon successively covers : the anterior aspect of the tibia, the anterior 

 capsular ligament of the tarsus, the pedal muscle, the anterior face of the 

 principal metatarsal, the articulation of the fetlock, and the two first phalanges. 

 It is covered by the tibial aponeurosis, and by three annular fibrous bauds which 

 maintain the tendon in the bend of the hock. One of these bands — the superior 

 — is fixed by its extremities to the tibia, a little above the tibio-tarsal articulation ; 

 it is common to the muscle we are describing, and to the flexor metatarsi. The 

 middle band, attached to the cuboid branch of the latter muscle and the inferior 

 extremity of the os calcis, is for the anterior extensor of the phalanges. The 

 inferior maintains the two extensors against the superior extremity of the 

 principal metatarsal. 



Action. — This muscle extends the digit and flexes the entire foot. 



2. Lateral Extensor of the Phalanges (Peroneus) (Fig. 201, 19). 



Synonyms. — Peroneo-prephalangeus— GiVard. The peroneus brevis of Man. (Tibio- 

 prephalangeus — Leyh.) 



Situation — Form — Structure — Extent — Direction. — Situated on the external 

 side of the leg, between the preceding and the deep flexor of the phalanges, it is 

 composed of a muscular portion and a tendon. The fii-st, elongated, prismatic, 

 and slightly penniform, extends in the direction of the leg, from the superior 

 extremity of that region to beyond its inferior extremity. The tendon succeeds 

 the lower end of the muscular portion, and traverses the groove on the middle 

 of the infero-external tuberosity of the tibia, passing to the external side of the 

 tarsus, where it is enclosed in a very firm sheath, and is inflected forwards to 

 become united to the tendon of the anterior extensor, near the middle of the 

 metatarsal region. 



Attachments. — It is attached, by the superior extremity of its muscular fibres, 

 to the external femoro-tibial ligament, to the whole extent of the fibula, and to 

 the fibrous partition which separates this muscle from the perforans — origin. It 

 terminates in the tendon of the anterior extensor. 



Relations. — Its muscular body is enveloped in a special containing aponeu- 

 rosis, which separates it, in front, from the anterior extensor, and behind from 

 the perforans. The tendon covers the tibia, and margins the external and 

 superficial ligament of the tibio-tarsal articulation ; this ligament suppHes a 

 fibrous ring for the formation of its reflected sheath. A bursa facilitates its 

 motion in the interior of this sheath. 



Action. — It acts Uke the preceding. 



