According to the Gurewitsch classification, the nucleus lenticularis was divided into areas of Pa (Putamen dorsalis anterior), Pd (Putamen dorsalis posterior), Pv (Putamen ventralis) and pallidum and the sizes of the nerve cells (long diameter) were measured. 1) The distribution of nerve cells varied in each area. 2) In each area of nucleus lenticularis excepting pallidum the long diameter of cells and their distribution curve were studied. The large cells, whose long diameter was greater than 24 μ, were regarded as GUREWITSCH effective cells and the other smaller cells as the receptive cells. 3) The large cells in each area of nucleus lenticularis decreased in order of Pd, Pv and Pa and their ratio to all nerve cells was Pd 2.1%, Pv 1.7% and Pa 0.9%. 4) The nerve cells in pallidum were morphologically quite different from those in putamen and most of them were such a kind of cells, whose long diameter was 20-24 μ, and its distribution curve showed a sharp peak.