SummaryThe splitting up of heterogeneous distributions into two normal componentsIt is shown that the frequency distributions of the nucleus volumes in various areas of the human cerebral cortex may be adequately described by two normal distributions superimposed on each other. The two normal components of the frequency distributions are found graphically by means of previously prepared sets of normal frequency curves. Curves of one set have the same mean and standard deviation, curves belonging to different sets have different standard deviations. The curves of one set have areas ranging from 10% to 100%.