The author explains the kinetogram's technique and says that the necessary movimentation results from a complex mechanism where various nervous circuits participate, emphasizing that lesions located on these circuits produce peculiar kinetographic distortions. He points out that from the beginning of some diseases of the central nervous system there are characteristic changes on the tracings. In one case of unilateral athetosis the author tries to explain the vicariant action of the normal homolateral cerebral hemisphere during simultaneous movements of both hands. Probably the Meynert's commissure is responsible for the interpallidal conduction of the vicariant control verified through the kinetograms. The reverberating and aberrant circuit which takes action on these conditions is discussed.