MUSCLES OF THE ANTEBIOB LIMBS. 267 



vessels and nerves. Its anterior border responds to the radius, A synovial 

 sheath envelops its terminal tendon, and facilitates its movements in the 

 fibrous canal through which it passes. 



Action. — It is a congener of the preceding. 



4. Superficial Flexor, Suhlimis of the Phalanges, or Perforatus. (Figs. 

 89, 119, 121, 122.) 



Sj/noni/ms.— EpitrocUo-phalangeus— Girard. ^Flexor pedis perforatus— FeraivaU 

 Humero-coronaris or humero-phalangeus — Leyh.) ' 



Situation.-^The superficial flexor of the phalanges is situated, with its 

 fellow, the perforans, beneath the flexors of the metacarpus, which form around 

 them a kind of muscular envelope. 



Form — Structure — Extent. — It is composed of a muscular and tendinous 

 portion. The first, long, thin, prismatic, and divided by a great number of 

 aponeurotic intersections, extends from the inferior extremity of the arm 

 nearly to the carpus. The tendon, continuous with the inferior extremity of 

 the muscular portion, receives at its origin an enormous fibrous production 

 that arises from the eminence of insertion situated at the posterior face of 

 the end of the radius, and which contracts somewhat intimate adhesions 

 with the antibrachial aponeurosis, as well as with the perforans. 



After being thus reinforced, this tendon passes through the carpal sheath 

 and arrives behind the fetlock, where it forms a ring (Fig. 89, 14) for the 

 passage of the tendon of the deep flexor. To this peculiarity is owing the 

 designations of perforatus and perforans, given to the two flexors of the * 

 phalanges. Afterwards it is inflected forwards over the sesamoid groove, 

 and terminates by two branches towards the middle of the digital region. 



Attachments. — It takes its origin, in common wiih the perforans, at the 

 summit of the i j]iw rl iii ii > uTi1 ij % and is inserted, by the bifurcations of its tendon, ,^ 

 into the extremities of the pulley formed behind the superior extremity of the '' 

 second phalanx. 



Relations. — The muscular portion, covered by the external and the 

 oblique flexors of the metacarpus, may be said to be incrusted in the perforans, 

 to which it adheres in the most intimate manner. The tendon covers that 

 of the latter muscle, and is in turn covered by the fibrous expansions of the 

 two metacarpal and metacarpo-phalangeal sheaths which are now to be 

 described. 



The Carpal sheath is the name given to a very remarkable annular 

 apparatus, formed by the superficial face of the common posterior ligament oi 

 the carpus, and by a thick expansion of inelastic white fibrous tissue, together 

 constituting a perfect arch thrown across like a bridge, from the supercarpal 

 bone to the inner side of the carpus. This arch is continuous, above, with 

 the antibrachial aponeurosis, and is prolonged, below, over the metacarpal 

 portion of the flexor tendons. An extensive synovial membrane covers the 

 internal aspect of the carpal sheath, envelops the perforatus and perforans 

 in their passage through this canal, ascends above the carpus, and descends 

 as far as the lower third of the metacarpal region. 



The Metacarpo-phalangeal sheath is formed by the sesamoid groove, the 

 posterior face of the principal navicular ligaments, that of the glenoid fibro- 

 cartilage of the first interphalangeal articulation, and by the posterior pulley 

 of the second phalanx. It is completed by a very wide membranous expansion 

 applied against the flexor tendons, closely adherent to the perforatus on the 

 median Mne of tho digit, and fixed, laterally, to the phalangeal bones by the 



