The alligator and its allies

by A. M. Reese

Muscles of the Forearm

Humero-radialis Internus (Radialis internus, Lange Vorwärtswender, Pronateur, Pronator teres, Pronator quadratus, Oberflächlich gelegener, langer runder Einwärtsdreher). This muscle arises from the condylus internus (C. ulnaris s. medialis) and attaches itself to the radius throughout almost its entire length. It is a fairly strong muscle.

Ulno-radialis (Carré pronateur, Pronator teres, Pronator quadratus, Muskel welcher dem Pronator quadratus entsprecht). A strongly developed muscle. It springs from the upper part of the flexor surface of the ulna and is inserted on the lower part of the flexor surface of the radius.

Humero-radialis Longus ([Plate II.], Figs. 1 and 2, 1) (Supinator longus, Long supinateur, Lange Rückwärtswender, Supinator radii longus). Among the Crocodilia this and the following muscle are well developed. This one springs from the condylus externus humeri and is inserted on the outer side of the entire length of the radius.

Humero-radialis Brevis ([Plate II.], Fig. 4, d) (Supinator brevis, Kurze Rückwärtswender, Extensor carpi-radialis brevis [?]). Arises near the preceding from the external condyle of the humerus and is inserted at the upper end of the radius.

Humero-carpi-radialis ([Plate II.], Fig. 2, a) (Aeusserer oder langer Speichenmuskel, Musculus quem parti superiori extensoris digitorum communis respondere videbat, Extensor carpi-radialis longus, Abductor pollicis longus). Towards the ulna, near the supinator longus muscle. It springs from the external condyle of the humerus, covers the supinator brevis muscle, and is inserted on the proximal end of the carpi-radialis.

Humero-carpi-ulnaris ([Plate II.], Fig. 2, c) (Extensor carpi-ulnaris, Ulnaris externus). Originates on the external condyle of the humerus, is inserted on the proximal end of the os carpi-ulnare.

Humero-metacarpalis III., IV., V. ([Plate II.], Fig. 2, b) (Extensor digitorum longus, Aeusserer Speichenmuskel or Speichenstrecker der Hand, Extenseur commun, Extensor radialis longus, Extensor digitorum communis). This muscle lies between the humero-carpi-radialis and the humero-carpi-ulnaris muscles. It springs from the condylus externus humeri and divides, on reaching the carpus, into three thin, flat tendons, which in part fuse with the carpo-phalangei muscle, and in part are inserted on the carpal bones of the third, fourth, and fifth fingers.

Carpo-phalangei ([Plate II.], Fig. 2, d). (Extensor digitorum brevis, Extenseurs courts, Gemeinschaftlicher Strecker der Hand, Extensor digitorum communis brevis). Springs from the carpal and, in part, from the metacarpal bones and is inserted on the terminal phalanges of the five fingers.

Ulno-carpi-radialis (Ein dem Strecker und Abzieher des Daumens analoger Muskel, Extensor pollicis longus, Extensor carpi-radialis brevior[?]). Springs from the under half of the ulna, and is inserted on the os carpi-radiale.

Carpo-phalangeus I. (Extensor pollicis brevis). This is a small, thick muscle that originates on the distal part of the os carpi-radiale and is inserted on the phalanx of the thumb.

Humero-radialis Lateralis ([Plate II.], Fig. 1, 6) (Flexor carpi-ulnaris, Innerer Ellenbogenmuskel, Ulnaris internus). A fairly strongly developed muscle. It springs from the internal condyle of the humerus, extends along the ulna, and is inserted on the proximal part of the os carpi-ulnare, and the nearby pisiform bone.

Humero-radialis Medialis ([Plate II.], Fig. 1, 2) (Flexor carpi-radialis, Radialis internus). A strongly developed muscle. It springs from the internal condyle of the humerus, receives fibers from almost the entire length of the radius, and is inserted on the proximal end of the os carpi-radiale and with a thin tendon to the metacarpal bone of the thumb. Rüdinger was not able to find this muscle in Alligator cynocephalus.

Carpo-phalangei ([Plate II.], Fig. 1, 4) (Flexor digitorum communis brevis, Oberflächlicher gemeinschaftlicher Fingerbeuger, Fléchisseur sublime, Flexores sublimis a profundo perforati, Lange Flexoren der Finger, Flexor digitorum communis sublimis s. brevis, Flexor digitorum sublimis). A small thick muscle. It springs from the ligamentum carpi-volare proprium and from the ulnar border of the distal end of the os carpi-radiale and is divided into eight muscle-bellies which pass over to the proximal ends of the first phalanges as thin tendons that are penetrated by those of the humero-ulno-phalangei muscle.

Humero-ulno-phalangei ([Plate II.], Figs. 1 and 2, 5) (Flexor digitorum communis profundus, Fléchisseur profond, Tiefer gemeinschaftlicher Fingerbeuger, Flexor digitorum profundus, Flexor profundus). Arises with three heads. The first head takes its origin from the internal condyle of the humerus, runs between the humero-radialis lateralis muscles, and passes as a tendon over to the carpus where it unites with the other two heads of this muscle. The second, deep head comes from almost the entire length of the ulna. These two heads may be called the long heads. The third, short head springs from the proximal ends of the two large carpal bones of the first row, and becomes united radially with the thick flat tendon ending the first two heads. The common terminal tendon splits into four points which pass among the tendons of the carpo-phalangei muscle and are inserted on the terminal phalanges. From the terminal tendons of this muscle spring the lumbricales muscles.

Carpo-phalangeus ([Plate II.], Fig. 1, 8) (Abductor pollicis). Springs from the os carpi-radiale; is inserted on the first phalanx of the thumb.

Carpo-metacarpalis I. ([Plate II.], Fig. 1, 9) (Opponens pollicis). Originates from the os carpi-radiale and is inserted on the radial side of the entire first metacarpus.

Metacarpo-phalangeus I. Originates from the base of the metacarpus of digit III.; is inserted on the ulnar side of the first phalanx of the thumb.

Pisiformi-phalangeus primus digiti V. ([Plate II.], Fig. 1, 7) (Abductor digiti minimi, Abducteur du petit doigt, Abductor digiti quinti). Springs from the pisiform bone, and is inserted on the medial border of the first phalanx of the fifth finger.

Carpo-metacarpalis V. (Opponens digiti minimi, Opponens primus). Springs from the carpi-ulnare bone and is inserted on the metacarpal bone of the fifth digit.

Carpo-phalangeus primus digiti V. ([Plate II.], Fig. 1, 3) (Flexor digiti minimi brevis, Opponens secundus). Arises from the ulnar border of the proximal part of the carpi-radiale bone and is inserted on the proximal end of the first phalanx of the fifth finger.

Metacarpo-phalangeus I. digiti V. (Adductor digiti minimi). Springs from the metacarpal bones of the second and third fingers and is inserted on the radial side of the first phalanx of the fifth finger.