These volumes consist mainly of a re-publication of the following papers -<br><br>"The Afferent Nervous System from a New Aspect," by Henry Head, W. H. R. Rivers and James Sherren (Brain, 1905, vol. xxviii. pp. 99-116).<br><br>"The Consequences of Injury to the Peripheral Nerves in Man," by Henry Head and James Sherren (Brain, 1905, vol. xxviii. pp. 116-340).<br><br>"A Human Experiment in Nerve Division," by W. H. R. Rivers and Henry Head (Brain, 1908, vol. xxxi. pp. 323-450).<br><br>"The Grouping of Afferent Impulses within the Spinal Cord," by Henry Head and Theodore Thompson (Brain, 1906, vol. xxix. pp. 537-741).<br><br>"The Automatic Bladder, Excessive Sweating and Some Other Reflex Conditions, in Gross Injuries of the Spinal Cord," by Henry Head and George Riddoch (Brain, 1917, vol. xl. pp. 188-263).<br><br>"Sensory Disturbances from Cerebral Lesions," by Henry Head and Gordon Holmes (Brain, 1911-12, vol. xxxiv. pp. 102-271).<br><br>"Sensation and the Cerebral Cortex," by Henry Head (Brain, 1918, vol. xli. pp. 57-253).<br><br>It was thought better to make no material change in their arrangement; for each of them deals with a definite theme and is concerned with some distinct aspect of the functions of the nervous system.<br><br>Each of these papers contained a short account of the methods employed in testing sensation; these I have excised and written a fresh chapter in which they are combined. I have also added an Introduction and an Epilogue dealing with the common aims which underlie these various researches.<br><br>Finally, some of the most serious criticisms of our researches on the functions of the peripheral nervous system have been considered in an Appendix at the end of the second volume.<br><br>I cannot close this short preface without expressing my thanks to all those who have collaborated with me. Without their help, so generously given, this work could not have been brought to a successful termination.