33 THE MUSCULAR SYSTEM. 
b. Abduction and Adduction. 
Lumbricales | 
Flexor brevis and WWemrons the inner side | 
| Opponens minimi | of the hand) | 
digiti | | 
| 
fom the middle ie the middle line 
Dorsal interossei J line of the middle | Palmar interosser J of the middle 
| finger) | finger) | 
Flexion is more powerful and complete than extension of the fingers. The flexor profundus 
alone acts on the terminal phalanges ; the flexor sublimis and flexor profundus together flex the 
proximal interphalangeal joint ; and flexion of the metacarpo-phalangeal artic ulation is effected 
by these muscles, assisted by the interossei, lumbricales, and flexor brevis minimi digiti. 
Extension of the phalanges is effected by the united action of the extensors of the digits, “the 
interossei and lumbricales ; extension of the fingers at the metacarpo- phalangeal joints is produced 
solely by the long extensor muscles. Separate extension of the index finger only is possible ; the 
three inner fingers can only be flexed and extended together, on account of the connecting bands 
joining the extensor tendons together on the back of the hand. 
5. Movements of the Thumb.—The movements of which the thumb is capable are flexion 
and extension (occurring at the carpo-metacarpal, metacarpo-phalangeal, and interphalangeal 
joints) ; abduction and adduction, together with circumduction (occurring at the carpo-metacarpal 
joint). 
ne muscles and pbcts Bespectives actions are given in eae following table :— 
a. Flexion and Extension. 
| Ouconenc: pollacis { (carpo-metacarpal Extensor ossis meta- { (carpo-metacarpal 
PI ie * (so. joint) | carpi pollicis joint) 
Flexor brevis cae Meee ANG y\) as oy .. ) (carpo-metacarpal and 
; ie Extensor brevis 
Adductors - metacarpo-phalangeal vain - metacarpo - phalan- 
Abductor J joint) ae a J geal joint) 
Flexor longus pollicis (all joints) _ Extensor longus pollicis (all joints) 
l. Adduction and Abduction. | 
| Adductors of the thumb | Abductor pollicis 
Flexor brevis | | ojicis _ Extensors of the thumb 
Opponens ! | 
First dorsal interosseous | 
ination of the above muscles. 
| 
| 
} 
The characteristic features of the movements of the upper limb are their range and 
refinement. The hand, in addition to its intrinsic powers, can be moved through a 
wide range and in several planes by the muscles acting on the wrist and radio-ulnar — 
joints ; this range is increased by the fore and aft movements at the elbow-joint, and the 
extensive movements of which the shoulder and clavicular joints are capable. The 
result is that the hand can be brought into a position to cover and guard any portion 
of the body. The precision and refinement of movement is made possible by the co- — 
ordinate movements of the various muscles acting upon the several joints, so that — 
actions can be performed (as eating) in which all the articulations of the limb are brought 
into play ; while others (such as writing) are possible by movements at the joints of the — 
wrist and fingers along with fixation of the elbow-joint. 
} 
THE LOWER LIMB. | 
FASCLEZ AND MUSCLES OF THE THIGH AND BUTTOCK. : 
FASCLA. i 
The superficial fascia of the thigh and buttock is continuous above with the — 
fascia of the abdomen and back, internally with that of the perineum, and below — 
with that of the leg. It presents noticeable features in the buttock and groin. 
