436 



THE MUSCULAK SYSTEM. 



slight gliding movement, occasioned by the action of the biceps and popliteus and the muscles 

 arising from the fibula. 



II. Movements at the Ankle-Joint. The movements at the ankle-joint are movements of 

 flexion and extension of the foot on the leg, along with inversion and eversion (only during 

 extension). These movements are produced at the ankle, aided by movements in the intertarsal 

 joints, and are occasioned by the following muscles : 



III. Movements of the Toes. A. At the Metatarso-Phalangeal Joints (assisted by move- 

 ments at the tarso-metatarsal and inter-metatarsal joints). These movements are flexion and 

 extension, abduction and adduction (in a line corresponding to the axis of the second toe). 



a. Flexion. 



Flexor digitorum longus 

 Quadratus plantae 

 Lumbricales 

 Flexor hallucis longus 

 Flexor hallucis brevis 

 Flexor digitorum brevis 

 Flexor digiti quinti brevis 

 Interossei 



Extension. 



Extensor digitorum longus 

 Extensor digitorum brevis 

 Extensor hallucis longus 

 Extensor hallucis brevis 





B. At the inter-phalangeal joints the movements are limited to flexion and extension. 



Movements of the Lower Limb generally. 



The characteristic features of the lower limb are stability and strength, and its muscles and 

 joints are both subservient to the functions of transmission of weight and of 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 

 from the sacrum through the posterior sacro-iliac ligaments to the hip bone, and through the 

 bones of the lower limb to the arch of the foot, where the talus distributes it backwards 

 through the calcaneus 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 corresponding 

 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 occur in the following way. At the beginning 

 of 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-joints, 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 



