the lower third of the humerus. Taking its origin by fleshy fibres alongside of the long head of the Biceps and the Coraco-brachialis, and receiving fibres from them, was a muscular slip, described as très mince in the Chimpanzee (Vrolik, 1. c.p. 19), which, after accompanying the long head of the Biceps for 212 inches, leaves it to be inserted into the humerus and intermuscular septum, immediately below the insertion of the Corecobrachialis, and alongside of the internal portion of the Triceps. This slip is not mentioned by Duvernoy as occurring in the Orang, but he found it in the Chimpanzee and Gorilla: in the latter, it joined the Dorso-epitrochlien. It did not occur in the Cebus or Magot, and Cuvier[1] has not figured it in any of his plates.
This slip is a frequent occurrence in the human subject, the Biceps being subject to many variations.
The Triceps differed from that of man only in having the long head of greater proportionate strength: it had a large insertion, covering a space of one inch and seven-eighths into the inner and lower edge of the scapula.
In examining the muscles which move the hand of the Orang, we find that, whilst the extensor muscles closely correspond with those of man, the flexor muscles are modified, in order to strengthen the hand for grasping, while the capability for varied and delicate movements must be impaired.
The Supinator Longus was large, its origin covering a space of 312 inches on the humerus, and some of its fibres appearing to interlace with those of the long head of the Triceps as it passed downwards.
The Extensor Carpi Radialis Longior arose from the external condyloid ridge of the humerus. The lower two-thirds of this muscle were tendinous: it was inserted into the radial side of the metacarpal bone of the index.
The Extensor Carpi Radialis Brevior was larger and stouter than the preceding muscle, and had a similar insertion into the metacarpal bone of the middle finger.
The Extensor Communis Digitorum presented almost exactly the same appearance as in man. In the Chimpanzee, according to Duvernoy, the portion for the index finger is distinct, from its origin.
The Extensor Minimi Digiti arose alongside of the Extensor Carpi Ulnaris from the ulna and intermuscular septum, passed through a distinct sheath of the annular ligament, and split into two tendons inserted into the ring and little fingers. In the Chimpanzee, it is inserted into the little finger only. The Gorilla has the tendon strongly connected with that of the Extensor Communis; the muscular portion seemed also to form part of the Extensor Communis. (Duvernoy, 1. c.p. 97.) In the Cebus, it formed part of the same muscular belly as the Extensor Communis, but soon separated from it, and was inserted as in the Orang. In the Magot, its origin, disposition, and insertion all resembled those in the Orang.
The Extensor Indicis, instead of being inserted only into the index, was flattened out, and inserted chiefly into the base of the
- ↑ Anat. Comp. Recueil de Planches de Myologie, dessinées par G. Cuvier.
