_a_, Common digital (or large metacarpal) artery; _b_, internal
metacarpal vein; _c_, internal metacarpal nerve; _d_, external
metacarpal nerve; _e_, branch of external volar metacarpal artery;
_f_, external metacarpal vein; _g_, _g_, _g_, deep volar or
interosseous metacarpal arteries; _h_, tendon of anterior extensor;
_i_, tendon of lateral extensor; _k_, anastomotic branch connecting
metacarpal nerves; _l_, deep flexor tendon; _m_, check ligament;
_n_, superficial flexor tendon; _o_, suspensory ligament; _p_, large
metacarpal bone; _q_, _q_, small metacarpal bones; _r_, skin (After
Ellenberger, in Leisering’s Atlas.)
]
6. The =internal volar= or =small metacarpal artery= (A. metacarpea
volaris medialis) is given off from the posterior radial at an acute
angle, usually a little above the external one or by a common trunk with
it. It passes down the inner side of the carpus behind the tendon of the
flexor carpi internus and embedded in the posterior annular ligament.
Arriving at the proximal end of the inner metacarpal bone it becomes
more deeply placed and is connected with the external volar artery by
one or two transverse branches as stated above. It then pursues a
flexuous course downward alongside of the inner small metacarpal bone,
like the corresponding external artery, with which it commonly unites as
described above. It is larger than the external artery and supplies the
nutrient artery to the large metacarpal bone.
The foregoing account describes the most common arrangement of the
dorsal and volar metacarpal arteries. Variations in their origin and
connections are common, but have no great surgical importance.
Collateral branches are omitted for the same reason. In some cases the
internal volar metacarpal is connected with the common digital or
large metacarpal artery a little below the carpus by a branch passing
obliquely across the inner border of the deep flexor tendon; this
forms a superficial volar arch.