THE LIMBIC system is comprised of the great limbic lobe of Broca and its subcortical cell stations. The limbic lobe, including the infolded hippocampus, was so named by Broca because it completely surrounds the hilus of the hemisphere. Its subcortical cell stations include the amygdala, the septal nuclei, the hypothalamus, the anterior thalamic nuclei, parts of the basal ganglia, and perhaps also the epithalamus. As Broca pointed out, the limbic lobe forms a common denominator in the brains of all mammals. In accordance with the theory of Papez, the experimentation of the last 15 years suggests that the limbic lobe also provides a cortical common denominator for a variety of emotional and viscerosomatic reactions in the mammal. Its relative constancy of gross and microscopic structure throughout the phylogeny of the mammal contrasts strikingly with the structure of the neopallium that mushrooms around it. The latter, some might argue, could be