The alligator and its allies

by A. M. Reese

Intermaxillaris and Sphincter Colli (Intermaxillaire, Mylo-hyoideus, Zwischenkiefermuskel, Latissimus colli). This muscle consists chiefly of transversely running fibers, and has in its middle third a small, median, longitudinal raphe or aponeurosis. In the posterior part of the neck it is very thin, but increases in thickness more and more as it passes cephalad. A short anterior and a long posterior portion may be distinguished. The former extends from the inner side of the right to that of the left half of the lower jaw, without a median aponeurosis. The hinder half of this muscle is united by a pair of aponeuroses to the lower jaw, on one hand (the smaller part), and to a fascia, on the other hand (the far larger part), that separates several of the neck muscles. The smaller part begins immediately behind the pterygoid on the inner side of the halves of the lower jaw but ends on the outer side of the two halves of the jaw.

Latus Colli (Latissimus colli accessorius). Lies underneath the preceding. Its muscle bundles lie between the collo-capitis muscle and the bodies of the first three cervical vertebræ, and form a broad band that extends from the hyoid bone to the backwardly directed cervical ribs of the first and second pairs.

Coraco-ceratoideus (Omo-hyoideus, Coraco-hyoideus). A long, narrow, and moderately thick muscle which takes its origin from the upper border of the coracoid, where the latter touches the scapula. It extends forward near the œsophagus and attaches itself to about the middle of the backwardly turned border of the horn of the hyoid of that side.

Episterno-ceratoideus (Niederzieher des Zungenbeins, or Brustbeinzungenbeinmuskel, Sterno-hyoideus). A flat and fairly broad muscle which springs from the ventral surface of the episternum; behind, it is separated by a slight space from the corresponding muscle of the other side, with which it nearly covers the cervical part of the trachea. Towards its anterior end it divides into two heads; one of these inserts itself on the outer border and outer surface of the cornu of the hyoid; the other head, lying laterad to the former, is suddenly reduced to a short tendon by which it is attached to the following muscle.

Maxillo-coracoideus (Mylo-hyoideus anterior, Sterno-maxillare). This muscle arises from the upper border and inner surface of the caudal third of the lower jaw. In its further course it becomes tendinous and projects by a short tendon outwards from the hyoid cornu to unite with the head of the preceding muscle, as noted above; it then becomes fleshy again and is inserted on the medial part of the upper border of the coracoid.

Maxillo-hyoideus (Genio-ceratoidien, Hyomaxillaris, Hyoglossus, Hyomandibularis, Mylo-hyoideus posterior). This muscle arises, very thin, from the mandibular symphysis, goes thence immediately backward and inward to insert itself, by its broad end, on the whole anterior end of the horn of the hyoid and on the hyoid itself.

Cerato-hyoideus. Arises from the horn of the hyoid and inserts itself on the body of the hyoid.

Costo-coracoideus. This muscle arises from the distal ends of the first and second ribs and is inserted on the ventral surface of the coracoid at the boundary of the scapula.

Costo-scapularis (Collo-scapularis superficialis, Levator scapulæ superficialis). See [shoulder muscles].

Costo-vertebralis Medialis (Scaleni). Fairly large, flat, and long-drawn-out three-cornered muscle. Attached by its base to the most anterior sternal rib, by its upper border to the fifth cervical rib, and by its point to the end of the second cervical rib.