AXIAL MUSCLES. 365 
B. At the inter-phalangeal joints the movements are limited to flexion and extension. 
Flexion. Extension. 
Flexor brevis digitorum (acting on the first | Extensor longus digitorum 
joint) | | 
Flexor longus digitorum (acting on both | Extensor brevis digitorum — | (acting on both 
joints) joints) 
Flexor longus hallucis (acting on the hallux) Interossei | | 
Lumbricales | 
| Extensor proprius hallucis 
| 
MovEMENTS OF THE LOWER LIMB GENERALLY. 
The characteristic features of the lower limb are stability and strength, and both its muscles 
and joints are subservient to the functions of transmission of weight and locomotion. In the 
standing position the centre of gravity of the trunk falls between the heads of the femora, 
and is located about the middle of the body of the last lumbar vertebra. It is transmitted 
through the bones of the lower limb to the arch of the foot, where the astragalus distributes it 
backwards through the os caleis to the heel, and forwards through the tarsus and metatarsus to 
the balls of the toes. 
Locomotion.—The three chief means of progression are walking, running, and leaping. In 
walking, the body and its centre of gravity are inclined forwards, the trunk oscillates from side 
to side as it is supported alternately by each foot, the arms swing alternately with the correspond- 
ing leg, and one foot is always on the ground. The act of progression is performed by the leg, 
aided in two ways by gravity. The movements of the leg are as follows :—At the beginning ot 
a step, one leg, so to speak, “shoves off;” the heel is raised and the limb is extended. By the 
action of the muscles flexing the hip and knee-joint, and extending the ankle-joint and toes, this 
limb is raised from the ground sufficiently to clear it, and passes forwards by the action of 
gravity, aided by the force given to the movement by the extensor muscles. After passing the 
line of the centre of gravity the flexion of the joints ceases, the muscles relax, and the limb 
gradually returns to the ground. The other limb then passes through the same cycle, the weight 
of the body now resting on the limb which is in contact with the ground. As the foot reaches 
the ground it, as it were, rolls over it; the heel touches it first, then the sole, and lastly, as the 
foot leaves the ground again, only the toes. In running, the previous events are all exaggerated. 
The time of the event is diminished, while the force and distance are increased. Both feet are off 
the ground at one time; the action of flexors and extensors alternately is much more powerful, so 
that on the one hand the knees are drawn upwards to a greater extent in the forward movement, 
and not the whole foot but only the toes reach the ground in the extension of the limb. The 
attempt is made to bring the foot to the ground in front of the line of the centre of gravity. At 
the same time the trunk is sloped forwards much more than in walking. In leaping, the actions 
of the limbs are still more exaggerated. The movements of flexion of the limb are still more 
marked, and the foot reaches the ground still further in front of the line of the centre of gravity. 
AXIAL MUSCLES. 
THE FASCIA AND MUSCLES OF THE BACK. 
THE FASCLH OF THE BACK. 
The general fascial investments of the back have been described (p. 507) 
along with the superficial muscles associated with the shoulder. The latissimus 
dorsi muscle has been described as arising in large part from the vertebral aponeu- 
rosis. This is a strong fibrous lamina which conceals the erector spine muscle. 
In the loin it extends from the spines of the lumbar vertebree outwards to the 
interval between the last rib and the iliac crest, where it is concerned in forming 
the lumbar fascia. Below the loin the vertebral aponeurosis is attached to the iliac 
crest, and more internally blends with the subjacent tendinous origin of the erector 
spine. The fascia can be followed upwards over the erector spine in the region of 
the thorax, where it is attached externally to the ribs and is continuous with the 
intercostal aponeuroses. In the lower part of the thorax it is replaced by 
muscular slips—the serratus posticus inferior; in the upper part of the thorax it 
ee beneath the serratus posticus superior and blends with the deep cervical 
fascia. 
The lumbar fascia is a narrow ligamentous band which connects the last rib to 
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