The movements of an animal generally and the mechanism which obtains and maintains its equilibrium usually give little thought to the onlooker. The beautifully arranged mechanism, however, by which associated muscles have their activities co-ordinated, has been largely explained by the illuminating researches of Sherrington. This book, which is based on original work by the Oxford School, unfolds step by step the manner by which the afferent messages which reach the spinal cord, ultimately give rise to efferent messages resulting in co-ordinated purposive responses in the muscles. The brain itself need take no part in these reflexes, which may be entirely mediated in the cord.