The =posterior radial= or =median artery= (A. mediana) is the direct
continuation of the brachial. It passes downward and slightly backward,
at first on the inner surface of the humerus, and then over the capsule
and internal lateral ligament of the elbow joint, under cover of the
posterior superficial pectoral muscle.[163] Below the elbow it dips
under the flexor carpi internus and passes down the inner part of the
posterior surface of the radius. In the distal part of the forearm it
inclines backward and is separated from the radius by the reinforcing
band (Caput tendineum) of the superficial flexor of the digit and is
continued by the large metacarpal artery.
It is accompanied by the median nerve, which lies in front of the artery
at its origin, then crosses over it obliquely at the elbow joint and
becomes posterior. In the arm the brachial vein lies behind and partly
upon the artery; lower down there are usually two satellite veins,
anterior and posterior. The chief collateral branches are as follows:
[Illustration:
FIG. 443.—DISSECTION OF LEFT FOREARM OF HORSE, EXTERNAL SURFACE.
(After Schmaltz, Atlas d. Anat. d. Pferdes.)
]