1909-10.] Short Muscles of the Hand of the Agile Gibbon. 203 
anterior annular ligament, and from the common head of origin of the 
opponens and the superficial head of the flexor brevis pollicis. 
Insertion. — Into the outer side of the base of the first phalanx of 
the thumb. 
Nerve Supply. — From the outer division of the median. 
Structure. — The muscle has a belly distinct from the other muscles of 
the thumb. The tendon is separate all the way to its insertion, and is 
the outer and most posterior of the tendons inserted into the first phalanx. 
Opponens Pollicis. 
This muscle is partly blended with the superficial head of the flexor 
brevis pollicis. 
Origin. — From the sesamoid bone or prepollex, scaphoid, trapezium, and 
outer part of the anterior annular ligament. 
Insertion. — Into the outer side of the first metacarpal. It is also 
prolonged down with the flexor brevis pollicis, from which it is at this 
point quite inseparable, to the outer side of the first phalanx. 
Nerve Supply. — From the outer division of the median. 
Structure. — The muscle is composed of short bundles of fibres running 
outwards and downwards. 
Flexor Brevis Pollicis. 
This muscle is composed of two heads, of which the superficial is partly 
fused with the last-mentioned muscle. 
Origin. — The superficial head. — By fleshy fibres from the scaphoid, 
trapezium and sesamoid bones, and by tendon (not shown in the plate) from 
the front of the anterior annular ligament. Deep head. — From the part of 
the trapezium which projects between the 1st and 2nd metacarpals, from 
the front of the base and the inner side of the 1st metacarpal bone. 
Insertion. — Into the sesamoid bone on the front of the 1st metacarpo- 
phalangeal joint ; the fibres are also prolonged downwards, to be inserted on 
the outer side of the shaft of the proximal phalanx. 
Structure . — The portion of the muscle which arises from bone is fleshy. 
The part of the superficial head which arises from the anterior annular 
ligament does so by thin tendons. These tendons end in small bellies, which 
join the rest of the muscle. The muscle is fleshy at its insertion. 
Short Muscles of the Little Finger. 
These are three small and relatively ill-developed muscles, which hardly 
form any prominence on the palm of the hand. 
