The waterproof sensory sheet covering the mammalian body has a rich afferent innervation which provides an abundance of complex information for use by the central nervous system often in conjunction with information from receptors in the joints. This book is an attempt to provide a systematic account of the way in which this somatosensory system works. The properties of the peripheral receptors have been debated in scientific terms for about a century and the resolu­ tion of the conflict in favour of the existence of 'specific' receptors for mechanical, thermal and noxious stimuli is reported and discussed in the opening chapters of the book. An awareness of this specificity has forced a re-consideration of the ways in which the central nervous system de-codes the information which is showered upon it. Advances in knowledge of the fine structure of the central nervous system have raised functional questions about the operation and organisation of the sensory systems in the spinal cord and brain. Fresh insight into the morphological complexity of the dorsal horn and higher levels of the nervous system gives the physiologist a clearer idea of the units with which he works. Progress has been made in understanding the function of sensory relay nuclei in general and indivi­ dual tracts in particular and is fully decomented.