368 THE MUSCLES OF THE DOG 



terior is the smallest. It has a fusiform belly in the proximal half of the leg and 

 arises from the grooved plantar surface of the fibula. The tendon joins that of the 

 flexor hallucis at the distal end of the leg. (2) The flexor digitalis longus is much 

 larger and has a fusiform, pennate belly which extends obliquely across the prox- 

 imal two-thirds of the leg. It arises from the proximal end of the fibula, the pop- 

 liteal line, the middle third of the medial part of the plantar surface of the tibia, and 

 the intermuscular septum between this muscle and the flexor hallucis. The ten- 

 don (which has a sjaiovial sheath) descends in a groove behind the medial malleolus, 

 bound do^^^l by an annular ligament, inclines laterally on the joint capsule, and 

 joins the tendon of the flexor hallucis. (3) The flexor hallucis has a large fusiform 

 belly which extends almost to the distal end of the leg. It arises from the greater 

 part of the plantar surface of the tibia, the medial surface and plantar border of 

 the fibula, and the interosseous membrane. The tendon descends in the tarsal 

 canal, receiving the tendons of the other heads, and ends like the corresponding 

 one of the forelimb. The tarsal synovial sheath begins at the distal end of the 

 muscular part and extends to the middle of the metatarsus. 



The lumbricales are absent, but there are four interossei. Rudimentarj^ 

 adductors of the second and fifth digits may be found. 



THE MUSCLES OF THE DOG 

 Muscles of the Face 



The cutaneus of the face is well developed. Most of it is a continuation of the 

 cervical cutaneus; the bundles extend forward over the lower part of the lateral 

 surface of the face to the angle of the mouth and the upper lip. Other bundles ex- 

 tend upward; some of these spread out on the cheek and lateral nasal region, and 

 a thin layer passes toward the lower eyelid, blending with the orbicularis oculi and 

 constituting a malaris muscle. Another stratmn is attached to the scutiform carti- 

 lage and spreads out, ort the rhasseter. 



The orbicularis oris is poorly developed. In the upper lip it is divided cen- 

 trally, and in the l6wer lip it is distinct only near the angles of the mouth. 



The levator nasolabialis is wide and undivided. It has an extensive origin on 

 the frontal and nasal bones. The fibers run downward and forward to the lateral 

 wing of the nostril and the upper lip. ■,.'', 



The levator labii superioris proprius arises behind the infraorbital foramen, 

 runs forward under the preceding muscle, and ends in numerous; Sniall 'tendons 

 which are in part inserted around the nostril, in part blend with those of the" oppo- 

 site side. . '■-':".; 



The zygomaticus is narrow and very long; it arises on the scutiform cartilage, 

 and ends at the angle of the mouth. 



The depressor labii inferioris is absent. ' .' :. 



There are no special nasal muscles. The honiologue of the lateral diljitor is 

 triangular; it is small at its origin just ventral to the levator labii; superioris~-pro- 

 prius, and ends almost entirely in the upper lip. :'..', • '. .' t 



The buccinator is wide and very thin, and the two planes of fibers^ cross 'each 

 other. ' ■'.'■■' 



The palpebral muscles present no very noteworthy special characters.'). Two 

 small muscles act on the upper eyelid. One of these, the corrugator supereilii, 

 arises from the fascia on the frontal bone and ends near the medial canthus. The 

 other arises from the zygomatic arch and ends near the lateral canthus. 



