Part 17

Action.—Contracting with the origin as the fixed point, they brace the skin over the forepart of the back. With the integumental attachment as the fixed point, they aid in the act of respiration.

=Cleido-trachealis.= Location.—Extending from the shoulder to the superior laryngeal region.

Origin.—From a small area on the antero-inner part of the middle of the arm of the furcula.

Insertion.—The fibers pass upward and become flattened and attached to the skin and dermo-temporalis muscle. They touch each other on the anterior border of the superior larynx, the trachea, and the skin over these parts.

Shape.—A slender bundle of muscles.

Relations.—Superiorly the skin, and internally the larynx and the trachea.

Action.—Controls the skin region of this part of the neck.

=Dermo-spinalis.= Location.—In the region of the shoulder.

Origin.—In an attenuated fascia from the crest of the neural spines of the first, the second, and the third dorsal vertebræ.

Insertion.—To the skin in a broad pale stratum, over the scapular region.

Shape.—Thin, pale, and very delicate.

Relations.—Superiorly with the skin, and inferiorly with the shoulder.

Action.—Controls the skin of the region.

=Dermo-iliacus.= Location.—Along the back on either side of the spine.

Origin.—From the inner angle of the marginal portion of the antero-dorsal border of the ilium.

Insertion.—Passing forward as a delicate band it spreads out and becomes lost in the skin of the shoulder region.

Shape.—Thin, delicate, and ribbon-shaped.

Relations.—Superiorly with the skin.

Action.—If the posterior end is fixed, it will cause the feathers to lie close to the skin. Its action would then be opposite to the dermo-dorsalis.

=Dermo-ulnaris.= Location.—Outer surface of the anterior upper costal and the posterior humeral region.

Origin.—By a thin fascia from the outer part of the third and the fourth true ribs at the base of their epineural appendages. Also from the fascia between them.

Insertion.—The fibers pass forward and upward as a thick muscular bundle and is loosely attached to the skin at a point just back of the humerus. The tendon later becomes spread out and attached to the fascia as far as the elbow-joint. It covers the olecranon of the ulna.

Shape.—At first rather thick, fascicular-like; later becomes tendinous; and at its attachment it becomes spread out over the olecranon.

Relation.—Inferiorly with the ribs and humerus, and externally with the skin.

Action.—A depressor of the humeral region.

THE SKELETAL MUSCLES

THE MUSCLES OF THE HEAD

Temporal Masseter Biventer maxillæ Entotympanicus Pterygoideus internus Pterygoideus externus Digastricus