The alligator and its allies

by A. M. Reese

The Muscles of the Scapula

Capiti-sternalis (Sterno-mastoideus). This is a fairly large muscle, on the side of the neck, that extends from the skull to the breast and from the middle of the neck is divided into two portions: (a) an anterior part or atlanti-mastoideus ([Plate I.], Figs. 1 and 2, cst¹) (upper end of the “head nodder,” sterno-mastoideus, anterior part of sterno-mastoideus, anterior part of atlanti-mastoideus); (b) a posterior part or sterno-atlanticus ([Plate I.], Figs. 1 and 2, cst²) (sterno-mastoideus, inner belly of the “head-nodder,” posterior part of the sterno-atlanticus). The former part is a rather short but not weak muscle that arises from the squamosum and inserts itself on the rib of the atlas (alligator) or of the atlas and epistropheus (crocodile).

The latter part is fairly strong and exceeds the anterior part in length; it springs from the rib of the first cervical vertebra, opposite the insertion of the anterior part, and inserts itself on the anterior border of the outer surface near the episternum. At times superficial fibers pass into the pectoral fascia.

Dorso-scapularis (Cucullaris) ([Plate I.], Figs. 1 and 2, Cu) (Trapezius). A broad but thin muscle that begins as an aponeurosis from the dorsal fascia in the middle line of the hinder part of the neck and beginning of the back; with converging fibers it passes within to insert itself partly on the spine of the scapula and partly by superficial fibers in the fascia that cover the deltoides scapularis inferior muscle.

Collo-scapularis Superficialis ([Plate I.], Fig. 1, cssp) (Levator scapulæ superficialis, Levator scapulæ, Heber des Schulterblatts, Acromio-trachélien, Teil des Serratus magnus, Levator anguli scapulæ). A considerable muscle on the side of the neck. It arises from the tips of the ribs of the first and second cervical vertebræ (where it is fused with the sterno-atlanticus muscle), and also from the transverse process of the third and fourth cervical vertebræ; it goes with diverging fibers to the entire anterior border of the scapula.

Thoraci-scapularis Superficialis (Serratus superficialis, Pectoralis minor, Hinterer Theil des inneren grösseren Rückwärtsziehers, Pars posterior m. serrati antici majoris, Theil des Grand dentelé, Serrati posteriores, Latissimus dorsi scapulo-costalis). A strong muscle of three prongs that go directly, by superficial fibers, over into the oblique abdominal muscle and meet the ribs. The first and smallest prong arises from the under end of the rib of the ninth vertebra (last cervical); the second and medium-sized prong comes from the uncinate process of the tenth rib (first thoracic) and from beneath the uncinate process of the second thoracic rib; the third and strongest prong takes its origin from the uncinate processes of the second and third thoracic ribs. All three prongs unite to form a broad, homogeneous muscle which passes forward and above to the hinder border of the scapula, upon whose entire surface, except at the lower end, it is inserted.

Collo-thoraci-suprascapularis Profundus ([Plate I.], Fig. 3, cthspr) (Levator scapulæ et serratus profundus, Serrati anteriores, Serratus anticus major, Vorderer Theil des inneren grösseren Rückwärtsziehers or vorderen grossen gezahnten Muskels, Pars anterior m. serrati antici majoris, Theil des Grand dentelé, Theil des Serratus magnus). This muscle arises in varying extent from the transverse process of the fifth cervical vertebra to the first (crocodile) or second (alligator) ribs. It is inserted on the inner surface of the suprascapula, except on its forward part, and is made up of two layers—a superficial and a deep one. The former layer ([Fig. 3], cthspr¹) is weakly developed and is composed of two or three thin, distinct bundles, that extend from the ribs of the eighth, ninth, and eleventh vertebræ (alligator) or from the transverse process of the seventh vertebra and the rib of the tenth. The deeper layer is considerably developed; its bundles come, in the alligator, from the fifth to tenth vertebræ; in the crocodile from the fifth to ninth.

Rhomboideus ([Plate I.], Fig. 3, rh) (Rautenmuskel, Angulaire de l’omoplate). This is a very small, independent muscle that springs, by two or three distinct bundles, from the fascia covering the longissimus dorsi muscle, in the region of the eighth and ninth vertebræ; after a short course it inserts itself on the antero-dorsal angle of the suprascapula.

Costo-coracoideus ([Plate I.], Fig. 3, cc) (Subclavius et Triangularis sterni and Levator secundæ superioris costæ, Petit dentelé, Pectoralis minor, Pectoralis). This is a broad muscle of considerable size on the ventral side of the breast; it consists of a lateral and of a medial portion, the former springing from the last cervical rib, the latter from the anterior border of the first sternocostal ridge. The two parts unite and are inserted on the whole posterior border of the coracoid.

Pectoralis minor (Pectoralis, Costo-coracoideus). A broad, considerable muscle on the under side of the breast, which is made up of two parts, of which the lateral springs from the anterior border of the last (ninth) cervical rib, and the medial from the anterior border of the first sternocostal ridge. Both parts unite into a homogeneous layer which is inserted broadly on the whole hinder border of the coracoid.