‘MYOLOGY., 67 
“The muscles situated on the outer and back part of the forearm are 
supinators and extensors, and may, like the last set, be arranged in a super- 
ficial and a deep layer. ‘The superficial consists of seven: supinator radia 
longus, extensor carpi radialis longus and brevis, extensor digitorum communis, 
extensor minimét digit, extensor carpi ulnaris, and anconeus. The deep mus- 
cles are five: the supinator radii brevis, three extensors of the thumb, and 
the indicator. 
~ Supinator radi longus, forming the prominence along the ofiter and ante- 
rior part of the forearm, arises from the external ridge of the humerus, and 
from the intermuscular ligament separating it from the outer head of the 
triceps. It is inserted into a rough surface on the outside of the radius, near 
its styloid process. It serves to roll the radius backwards and to bend. the 
elbow joint. 
- Ketensor carpi radials longus arises from the ridge on the external side of 
the humerus, and is inserted into the back part of the metacarpal bone of 
the index finger. 
Extensor carpi radialis brevis arises from the inferior and posterior part of 
the external condyle, and from the external lateral ligament; it is inserted 
into the carpal extremity of the third metacarpal bone (that of the middle 
finger). 
( Hetensor digitorum communis arises with the last and the extensor minimi 
digiti, from the external condyle and from the ulna. About the middle’ 
of the back of the forearm it ends in four muscles, each ending in tendons, 
which pass under the annular ligament and are inserted into the phalanges 
of the four fingers. It serves to extend all the joints of the fingers, as also 
the carpus. 
Hetensor carpi ulnaris arises from the external condyle, fascia, and inter- 
muscular septa, and ends in a strong tendon, which is inserted into the 
carpal end of the fifth metacarpal bone. It extends and bends back the 
hand, and adducts or flexes it laterally towards the ulna. 
Anconeus is placed at the outer side of the olecranon, beneath the skin, 
and arises from the posterior and inferior part of the external condyle and 
lateral ligament, and is inserted into the external surface of the olecranorr, 
and the superior fifth of the posterior surface of the ulna. Its use is to 
extend the forearm on the arm. 
Extensor minimi digitt vel auricularis arises in common with the extensor. 
communis, and is inserted with the fourth tendon of this muscle into the 
posterior part of the phalanges of the little finger. It assists the extensor 
communis, and can extend and abduct the little finger independently of the 
rest. 
Supinator radu brevis surrounds the upper part of the radius: it arises 
from the external condyle, external, lateral, and coronary ligaments, and 
from the outer side of the ulna, and is inserted into the external and ante- 
rior surface of the radius. It turns the radius outwards, so as to supinate 
the hand. 
Fixtensor ossis metacarpr pollicis, or abductor pollicis longus, arises from 
the middle of the posterior part of the ulna and posterior surface of the 
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