This study was performed by means of cinephotography and electromyography. The results were correlated with earlier investigations concerning the forces exerted by the pads of walking dogs. A concept about the action of individual muscles of the hind limb during a stride was formed. The principal conclusions are: (1) The hamstrings are divisible into a cranial and a caudal group, the first consisting of the cranial parts of the M. biceps femoris and M. semi-membranosus, the second of the caudal parts of these muscles, together with the M. semitendinosus. The chief function of both groups is to extend the hip; the caudal group also flexes the stifle. (2) Activity is present in the greatest number of muscles during the change in the sense of movement of the limb. (3) During the last stages of the stance phase the number of muscles showing electrical activity diminishes, while the force exerted by the pads in a horizontal direction increases. Non-muscular forces, e.g. inertia, play an important role during movement.
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