This section will consider the structure and function of muscle receptors, as well as the central nervous system mechanisms with which they are concerned. In volume I of this Handbook, receptor mechanisms are discussed in detail. Also, the crustacean stretch receptor and the frog muscle spindle have been considered. The present section will be concerned with vertebrate muscle receptors with an emphasis on mammals. Muscle receptors provide interesting examples of specialized mechanorecep­ tors. The muscle spindle is a striking case of a receptor which is regulated in its function by the central nervous system in efferent neurons. Muscle receptors have long been known to playa crucial role in the reflex regulation of movement. In recent years it has become apparent that these receptors are also important in sensory phenomena such as the perception of position and movement. St. Louis, July 1974 c.c. HUNT Contents Chapter I The Morphology of Muscle Receptors. By D. BARKER. With 99 Figures . . . . . . . . . . . . . . . .. 1 Chapter II The Physiology of Muscle Receptors. By C.C. HUNT. With 21 Figures . . . . . . . . . . . . . . . . . 191 Chapter III Central Actions of Impulses in Muscle Afferent Fibres. By A. K. McINTYRE. With 8 Figures 235 Author Index 289 Subject Index 299 List of Contributors BARKER, David Department of Zoology, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, Great Britain HUNT, Carlton C. Department of Physiology and Biophysics, Washington University, School of Medicine, 660 South Euclid Avenue, St. Louis, Mo. 63110, USA McINTYRE, A. K.