NEAR THE end of the last century, Golsinger (1895), cited by Roussy,1 presented the brains of six dogs with isolated lesions produced by unipolar electrolysis with a current of 20 to 40 ma. Sellier and Verger2 (1898) made their small lesions deep in the brains of three dogs with a bipolar electrode passing a current of 9 to 15 ma. for 7 to 10 minutes. Horsley and Clarke3 (1908) studied carefully some of the physical principles involved in such a use of electrodes and demonstrated that much less gas was evolved, and in a less explosive manner, at the anode than at the cathode; hence their anodal lesions were more constant in size than those produced at a cathode or with a bipolar electrode. After many observations, they ventured the statement that for a unit of time, "e. g., one minute, there will result about 1 mm.