The present study deals with the electrogram of the midbrain tegmentum in man and the influence of this region upon the electromyogram and the electroencephalogram, chiefly in Parkinsonian patients; it is part of a project attempting to influence static tremor, rigidity, and spasticity by placing lesions in an area remote from the pyramidal tract. Pallidal, as well as thalamic, lesions performed for the relief of these conditions may interfere with the function of the corticospinal pathway either by directly encroaching upon fibers of the internal capsule or by disturbing their blood supply. In order to avoid such a possible interference, the tegmentum of the rhombencephalon and mesencephalon seemed to offer a suitable location; in this region extrapyramidal fibers descend, and it contains in its so-called reticular formation cell groups which represent supraspinal centers of the static innervation (Spiegel and Bernis,1 1925, Magoun,2 1948); this innervation, when distorted, may