Applied anatomy and kinesiology, the mechanism of muscular movement . ther flexors and themusculospiral the other extensors. Interesting light is thrown onthe action of these muscles by the forms of paralysis resulting fromdisease and injury of these nerves. Ulnar paralysis frequently involves the lumbricales and inter-ossei. When these muscles are paralyzed, especially when no othermuscles are involved, the hand takes the claw-like form shown inFig. 86. The explanation is that when the normal tone of lumbri-cales and interossei is gone the unopposed tension of the extensorcommunis pulls the f
Applied anatomy and kinesiology, the mechanism of muscular movement . ther flexors and themusculospiral the other extensors. Interesting light is thrown onthe action of these muscles by the forms of paralysis resulting fromdisease and injury of these nerves. Ulnar paralysis frequently involves the lumbricales and inter-ossei. When these muscles are paralyzed, especially when no othermuscles are involved, the hand takes the claw-like form shown inFig. 86. The explanation is that when the normal tone of lumbri-cales and interossei is gone the unopposed tension of the extensorcommunis pulls the first phalanx into a position of overextensionwhile the flexors sublimis and profundus for the same reason producepronounced flexion of the other two phalanges. Any attempt of 148 MOVEMENTS OF THE HAND the patient to flex or extend his fingers only exaggerates the deform-ity. The hand is useless, for without the ability to flex the firstphalanx it is impossible to close the hand or grasp anything betweenthe fingers and thumb. Recovery frequently occurs, and then the. Fig. 86.—Claw-shaped hand resulting from paralysis of the Iumbricales and interosseicaused by an injury to the ulnar nerve. (Duehenne.) claw form is gradually lost and the posture of the normal restinghand resumed, as the small muscles gradually take on normal vigorand tone. Another condition that makes it impossible to close the hand orgrasp an object with fingers and thumb is paralysis of one or bothof the long flexors of the fingers. Fig. 87 shows the effect on theposture of the hand of paralysis of the middle half of the flexor
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