CHAPTER I
INTRODUCTION
This book contains a series of researches into the physiology of the nervous system based on clinical observations. Each section of the work formed the subject of a separate communication published at various times in Brain; but they have been rearranged so as to comprise an orderly sequence extending from the peripheral nervous system to the receptive centres of the cortex.
Throughout the last eighteen years, occupied by these investigations, I have had the inestimable advantage of collaborating with fellow-workers each of whom was an expert in his own aspect of the subject. Any one who compares the various portions of this book will recognise how greatly the work has gained by this diversity of outlook, and I cannot be sufficiently grateful to my colleagues for all they have taught me. Our observations must of necessity contain errors; but these would have been many times more numerous if I had not had the assistance of their expert knowledge.
But in spite of the diversity of outlook evident in each section of this book, certain basic principles guided us throughout and served to weld its various portions into a coherent whole. These may be summarised under the following headings.
1. The Tests employed must yield Measurable Results.
Throughout we have attempted to employ tests which yielded measurable results. In the case of the experiment on my arm this presented no difficulty; we adopted, with certain modifications, the methods already in current use in the psychological laboratory. For we were not hampered by lack of time or opportunity. A set of observations which failed on one day could be repeated on some subsequent occasion, and multiplied almost to any extent. We were not compelled to consider the wishes of the patient, and had no solicitude as to his good will.
As the outcome of these elaborate experiments on my arm and with the gradual progress of our knowledge we were able to evolve a series of tests applicable to the less favourable conditions of clinical research. These are described fully in Chapter II.
The results of these tests could be expressed in measured terms; we eliminated as far as possible uncorroborated opinion. But no such measurements in pathological states can be of any value without some comparable
