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 synovial sheath) descends in a groove behind the medial malleolus, 
bound down 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. Rudimentary 
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 stratum is attached to the scutiform carti- 
lage and spreads out on the masseter. 
The orbicularis oris is poorly developed. In the upper lip it is divided cen- 
trally, and in the lower 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 ran 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 small 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 homologue of the lateral dilator 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. 
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 supercilil, 
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. 
