THE MUSCLES OF THE HEAD. 105 



lis (r). The aponeurosis is united with the caudoventral angle 

 of the scutiform cartilage and with the ventral edge of the 

 cranial margin of the auricular cartilage. 



This muscle is united at its cranial end with the orbicularis 

 oris (/) ; throughout its length more or less with the platysma 

 {a, a'); at its caudodorsal end with the corrugator supercilii 

 lateralis [k) on its medial side, and with the submentalis {c) on 

 its lateral side. 



Relations. — Outer surface with the integument and the 

 platysma [a'). Inner surface with the masseter, temporal, 

 frontoscutularis, and adductor auris inferior [o). 



Action. — Draws the angle of the mouth dorsocaudad ; the 

 external ear ventrocraniad. 



M. submentalis (Fig. 64, c). — A flat band, similar to the 

 last, and closely connected for some distance to its caudal 

 border. 



It arises as scattered fibres near the ventral middle line at 

 about the level of the laryn.x, the fibres of the opposite muscles 

 crossing the middle line and intermingling. The fibres pass 

 dorsad, converging so as to form a narrower band, which 

 unites dorsad with the zygomaticus {d), to be inserted with it 

 into the tendinous aponeurosis above described. 



Relations. — Outer surface with the integument and pla- 

 tysma {a'). Inner surface with the muscles of the hyoid, the 

 digastricus, the parotid gland, the masseter, the zygomatic arcli 

 and the temporal muscle. 



Action. — Draws the external ear ventrad. 



M. depressor conchae (Fig. 64, b). — A thin band of fibres, 

 caudad of the last and parallel with it. The muscle arises as 

 scattered fibres on the ventral surface of the neck, one or 

 two centimeters craniad of the manubrium, the fibres of the 

 muscles of opposite sides crossing the middle line and inter- 

 digitating. They pass dorsad, gathering together to form a 

 narrow band which is inserted into the summit of the antitragus. 



Relations. — Outer surface with the skin at the ventral end, 

 and with the platysma {a') further dorsad. Inner surface with 

 the deep muscles of the neck and with the parotid gland. 



Action. — Draws the external ear ventrad. 



