. A manual of diseases of the nervous system. terferes 48 ACTION AND PARALYSIS OF MUSCLES. with walking, since the knee-joint cannot be bent, in the forward movement ofthe leg, until the thigh is flexed sufficiently to permit the weight of the foot toflex the knee. To prevent the toes striking the ground the foot is unduly flexedon the leg. The loss of the support that the flexor tendons give to the knee-joint leads to an undue strain on the ligaments, which become stretched, andslight retroflexion of the joint may occur. In paralysis of the muscles that extend the hip, there is a tendency to
. A manual of diseases of the nervous system. terferes 48 ACTION AND PARALYSIS OF MUSCLES. with walking, since the knee-joint cannot be bent, in the forward movement ofthe leg, until the thigh is flexed sufficiently to permit the weight of the foot toflex the knee. To prevent the toes striking the ground the foot is unduly flexedon the leg. The loss of the support that the flexor tendons give to the knee-joint leads to an undue strain on the ligaments, which become stretched, andslight retroflexion of the joint may occur. In paralysis of the muscles that extend the hip, there is a tendency to fallforwards in walking. To counteract this the trunk is carried backwards, and afatiguing strain on the flexors of the hip results. In paralysis of the biceps, the leg, during flexion, is rotated inwaids; whenthe biceps remains and the other muscles are paralysed, there is an undue rota-tion outwaids. The effect of these abnormal movements on the ligaments of Tibialis anticus,Extensor digit Peroneus brevi Extensor long, po: Dorsal interosse. Ext. poplit. n. Gastrocnem. (outer head).Peroneus longus. Soleus. Flexor long. poUicis. Extensor brev. digit. Abductor minim, digit. Pia. 26.—Motor points of leg, outer side (Erb). the joint is such that, after a time, the amount of rotation becomes greater thanis possible in health. The Popliteus (internal popliteal nerve) has but a feeble power of flexing theknee. Its chief action is to rotate the leg inwards when the knee-joint has beenflexed. Muscles movhto the Foot.—Extensors of Foot on Leg*—The Gastro-cnemius and Soleus (internal popliteal branch of the sciatic—L. 5 and S. 1) • These muscles are sometimes termed plantar flexors,** because they are homo*logons with the flexors of the wrist. The term is a bad one, since it involves a nse MUSCLES OP LOWER LIMB. 49 have the same action. They extend the hinder part of the foot and draw downthe outer side of the forepart of the foot, but very little the inner side. Hencethe foot
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