The following research was carried out in consequence of suggestions made to me by Professor Victor Horsley, to whom I wish to express my thanks for placing the facilities of his laboratory at my disposal, and for his advice and criticisms during the prosecution of the work and in the preparation of the paper. I also wish to return my best thanks to Professor Johannes Gad, in whose laboratory tire first part of the work was carried out, for his ever-ready and constant help and advice. I have further to thank my friend Dr. Risien Russell for his kindness in assisting me in some of my earlier experiments on the monkey. The researches were undertaken with the view of throwing light upon the degree to which certain movements or, speaking more precisely, sensori-motor (kinæsthetic) phenomena are represented in any given segment of the lumbo-sacral region of the mammalian spinal cord, and further what relationship exists between the representation of one movement and that of another. It is clear that at least three methods suggest themselves as means whereby this problem may be attacked,
e. g.
, (1) the excitation method, (2) the method of exclusion by ablation, and (3) the so-called degeneration method. Of these Nos. (2) and (3) have been already in part employed (No. (2) Sherrington, Risien Russell, No. (3) Grünbaum), but believing that with suitable precautions more exact localisation could be obtained by the excitation method, I have so far adopted that alone.