380 THE MUSCLES OF THE DOG 



The capsularis is usually present, but is small and pale. 



The sartorius consists of two parts. The anterior part arises from the tuber 

 coxse and its flat tendon ends on the patella. The posterior part arises from the 

 lateral border of the ilium and ends on the medial surface of the tibia, its tendon 

 blending with that of the gracilis. The anterior part is superficial in front of the 

 tensor fasciae latae and forms here the anterior contour of the thigh. 



The graciles are not so much fused at their origin as in the other animals. 

 Its anterior part is thin. Its broad tendon is inserted into the tibial crest, and 

 blends with those of the sartorius and semitendinosus. 



The pectineus is long and slender. It arises from the ilio-pectineal eminence 

 and ends on the medial branch of the Hnea aspera above the distal end of the femur. 



The adductor femoris is a large muscle which arises on the ventral surface of 

 the pubis and ischium; it ends on the linea aspera of the femur and the medial 

 surface of the stifle. It is commonly separable into two parts. 



The peroneus tertius is represented by a tendinous band which arises on the 

 medial surface of the tibia below the crest. It passes on the medial surface of the 

 tibialis anterior, blends with the annular ligament above the tarsus, and is attached 

 to the joint capsule and the proximal end of the third metatarsal bone. 



Arloing and Lesbre say: "The third peroneus is a proper extensor of the fifth digit; it 

 is a verj' feeble, fleshy band, situated behind the peroneus brevis, which it partially covers. It 

 is attached to the upper part of the fibula, and is continued by a long, delicate tendon which 

 passes in the same malleolar groove with the muscle mentioned ; it then crosses behind the tendon 

 of the peroneus longus and extends to the phalanges of the outer digit, where it joins one of the 

 branches of the common extensor." 



The tibialis anterior is large and superficial. It arises on the lateral condyle 

 and crest of the tibia, and is inserted into the first metatarsal bone, or into the 

 first tarsal and second metatarsal. 



There are four extensors of the digits. 



1. The long digital extensor (M. extensor digitalis longus) is fusiform, and lies 

 largely under the preceding muscle. It arises from the extensor fossa of the femur. 

 The tendon is bound down by two annular ligaments: the proximal one, at the 

 distal end of the tibia, encloses also the tendon of the tibialis anterior; the distal 

 one is at the lower part of the tarsus. The tendon divides at the tarsus into 

 four branches, which end on the distal phalanges of the digits (second to fifth). 



2. The lateral digital extensor (M. extensor digitalis pedis lateralis s. digiti 

 quinti) has a small, unipennate belly which is covered by the peroneus longus 

 and the deep digital flexor. It arises on the fibula below the head. The tendon 

 descends behind that of the peroneus longus, inclines forward under the lateral 

 ligament of the tarsus and the peroneus tendon, and joins the branch of the 

 tendon of the long extensor for the fifth digit. 



3. The extensor hallucis longus is a very thin muscle which arises from the 

 fibula under the long extensor. Its delicate tendon accompanies that of the tibialis 

 anterior to the first metatarsal bone, or becomes lost in the fascia. 



4. The extensor digitalis brevis has three divisions. It arises on the fibular 

 tarsal bone and the adjacent ligaments. The three tendons are inserted into 

 the second, third, and fourth digits, blending with the interossei. (Sometimes 

 there is a tendon for the rudimentary first digit, which may represent the extensor 

 hallucis brevis. There may be a fourth belly for the tendon to the second digit.) 



The peroneus longus arises on the lateral condyle of the tibia, the head of 

 the fibula, and the lateral ligament. The belly does not extend to the middle of 

 the leg, and the long tendon passes down the leg parallel to the fibula. It is bound 

 down in the groove of the lateral malleolus by an annular ligament, crosses the 

 plantar surface of the tarsus transversely, and ends on the first metatarsal bone. 



The peroneus brevis is unipennate and arises from the distal half or more 



