of the stimulus whether only a part or the whole of these movements resulted. Similarly, with regard to the lateral extent of the areas mentioned above, although, of course, a strong stimulus caused movement in all parts named, yet in each case it was quite definite that the area, stimulation of which produced movement in the tail, was nearer the middle line than that for the hamstrings, the area for the hamstrings nearer the middle line than that for flexion of the hip, and this median of that which caused lateral flexion of the side. Hence these results demonstrate from a functional standpoint the anatomical arrangement which has been described by various writers—Ramon-y-Cajal, Kolliker. Golgi, &c.
As in the dog, the knee jerks were found not only present, but even exaggerated, after the cord had been completely divided.
Also section of the cord caused increased excitability of the parts below section, but abolished the movement produced by stimulation of the first or second or third posterior roots below the level of the section, and the more oblique the position of the posterior root fibres in contact with the cord, the greater the interval affected in this manner.
On the Production of Movement by Stimulation of the Anterior and Posterior Spinal Roots in the Monkey.
The general results obtained by excitation of the spinal roots in the monkey were the same as those in the dog. As already known (Sherrington, Risien Russell) stimulation of the third lumbar to the first or second sacral anterior roots (inclusive) alone produces movement in the lower limb, yet, on stimulation of the posterior roots of the twelfth dorsal to the second sacral inclusive, it was found that movement resulted in the lower limb, and in the latter case the bulk of the movement produced is that of flexion.
Summary and Conclusion.
1. Relationship of Posterior Roots to Reflex Kincesthetic Centres.—It appears from the foregoing experiments to be definitely established that any reflex centre derives its chief afferent impulses from a nerve root which enters the cord, as a rule, about two segments higher, i.e., on the cephalic side. This generalisation, established by the method of excitation, is confirmed by anatomical and pathological considerations.
2. Lateral Arrangement of Fibres in Burdach’s Column.—The fibres of the postero-external column are arranged in a definite and constant order from within out, the innermost fibres (i.e., those nearest the middle line) representing the most distal portions of the tail and lower limb and the outermost the proximal segments of the limbs.
