THE LIMBS OF THE HORSE L37 



the third and fourth metatarsal bones, and crosses the tendons of the 

 extensor digitorum longus and peronrcus longus. 



A fourth and less definite transverse ligament retains the tendon of 

 the peromvus longus in the groove on the surface of the lateral 

 malleolus. 



The muscles in the region now being examined are five in number, 

 namely, extensor digitorum longus, tibialis anterior, peronseus longus, 

 peronseus tertius, and extensor digitorum brevis. Two of these — 

 peronreus tertius and tibialis anterior — are so blended as to lead the 

 uninstructed to assume that they form one muscle only. 



M. BXTBNSOE digitorum longus. — The long digital extensor arises 

 from the depression on the femur between the patellar surface and the 

 lateral condyle by a strong tendon that is common to this muscle 

 and the peronseus tertius. The tendon of origin traverses the muscular 

 notch lateral to the tuberosity of the tibia, and is succeeded by an 

 elongated, spindle-shaped belly that extends into the distal third of 

 the leg. From this point a flattened tendon, held in position by the 

 three fascial bands (transverse ligaments) mentioned above, crosses the 

 flexor aspect of the tarsus, where it is provided with a synovial sheath, 

 and travels along the dorsal aspect of the metatarsus and digit to be 

 inserted to the extensor process of the third phalanx. In the proximal 

 third of the metatarsus the tendon is joined by the extensor digitorum 

 brevis and the tendon of the peronseus longus. Otherwise its con- 

 nections and general disposition resemble those of the tendon of the 

 common digital extensor of the thoracic limb (q.v.). 



M. peronseus longus. 1 — The long peroneal is the most lateral 

 muscle of the leg, and follows the line of the fibula between the 

 muscle just described and the flexor hallucis longus. Its origin is from 

 the lateral (fibular) collateral ligament of the femoro-tibial joint, the 

 fibula, and the interosseous ligament between the tibia and the fibula. 

 The tapering fleshy belly gives place to a rounded tendon, which passes 

 along the groove on the lateral malleolus and through a sheath on the 

 lateral aspect of the tarsus. About the junction of the proximal and 

 middle thirds of the metatarsus the tendon joins that of the long 

 digital extensor at an acute angle. 



M. extensor digitorum brevis. — The short extensor of the digit 



is a small, pale, flattened muscle occupying the angle formed by the 



converging tendons of the long extensor and long peroneal muscles. 



Its origin is from the lateral limb of the tendon of insertion of the 



peronseus tertius and the lateral (fibular) collateral ligament of the 



tarsus. 



1 This muscle is also known as the lateral digital extensor, a proceeding which 

 is permissible on account of its doubtful homology. 



