Chapter IV: Muscles of the Neck and the Deep Muscles of the Head

If the superficial muscles of the head have been dissected according to the directions above given (p. 434), the skin of the head and neck, and the external ear, will have been removed, and the specimen is ready for further study. The parotid and submaxillary glands (Fig. 65, 1 and 2) should be removed if this has not been done; also the lymphatic glands (Fig. 65, 3).

If the superficial muscles of the head have not been dissected and are not to be, remove the skin from the side of the neck, head, and face to the median dorsal line, removing the thin superficial muscles with the skin. Remove also the parotid, submaxillary, and lymphatic glands (Fig. 65, 1, 2, and 3), and cut through the ear-muscles and the cartilaginous auditory meatus (under direction) and remove the external ear. Clean fat, connective tissue, etc., from the surface of the muscles of the thorax, neck, and head; then dissect as follows:

1. The sternomastoid (p. 139, and Fig. 65, _g_). Transect and reflect it.

2. The cleidomastoid (p. 120, and Fig. 65, _h_). This has already been transected; examine now its origin.

Remove the large lymphatic gland beneath the sternomastoid and close to the tympanic bulla, and clean the surface of the muscles in this region.

3. The levator scapulæ ventralis (p. 120, and Fig. 72, _c_, _c′_, _c″_). This has already been cut; study now its origin.

4. The sternohyoid (p. 140, and Fig. 65, _e_). In raising it begin at the cranial end and take care not to injure the subjacent sternothyroid (Fig. 65, _g′_). Transect.

5. The sternothyroid (p. 141, and Fig. 65, _g′_). Transect.

6. The stylohyoid (p. 112, and Fig. 65, _d_). Transect.

7. The digastric (p. 107, and Fig. 65, _b_). Transect, and reflect completely, to the origin and insertion.

8. The mylohyoid (p. 114, and Fig. 65, _c_). Transect and reflect.

9. The geniohyoid (p. 113, and Fig. 67, _g_).

10. The jugulohyoid (p. 113, and Fig. 67, _b_).

(The extrinsic muscles of the tongue (p. 228, and Figs. 67 and 96) may be dissected at this point, if desired. (_a_) The styloglossus; (_b_) the genioglossus; (_c_) the hyoglossus. They need not be cut.)

11. The masseter (p. 108, and Fig. 65, _a_). Cut the superficial and middle layers near their insertions by incisions parallel to the border of the jaw. Cut the deep layer near its origin. Look for the origin of fibres of the temporal muscle from the inner surface of the middle layer.

12. The temporal (p. 110, and Fig. 63, _n_). Clear its outer surface completely. Cut the temporal fascia transversely and reflect it toward the insertion of the muscle, with the superficial portion of the muscle. Cut through the zygomatic arch at its two ends and remove it, dissecting the fibres of the temporal free from their origin on its inner surface. Then examine the insertion of the temporal.

(The muscles of the pharynx (p. 232) may be dissected at this point; for directions, see page 451.)

13. The ceratohyoid (p. 115). To uncover this, the middle constrictor of the pharynx (Fig. 67, _j_) must be cut and reflected.

Cut the mylohyoid, geniohyoid, genioglossus, and the mucosa of the floor of the mouth free from the mandible on both sides, so that the tongue and the floor of the mouth may be drawn ventrad and turned out of the way, exposing the roof of the mouth (as in Fig. 66, p. 112). Cut through one side of the pharynx near the ventral surface and turn the tongue toward the uncut side.

The roof of the mouth is thus exposed. Dissect next--

14. The pterygoid muscles (Fig. 66). Remove the mucosa of the roof of the mouth, especially at the sides of the soft palate, and the two pterygoid muscles (p. 111) are exposed. The lower jaw may be removed on one side to get at their origin.

(The muscles of the soft palate (p. 230, and Fig. 66, _d_ and _e_), and the superior constrictor of the pharynx (p. 233, and Fig. 66, _f_) may be observed at this point, if desired.)