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Article
April 8, 1899

THE BRAIN AND ITS FUNCTIONS.A SUMMARY. PART I.

JAMA. 1899;XXXII(14):751-755. doi:10.1001/jama.1899.92450410011002b
Abstract

The part of the brain which has been most studied is its gray-matter covering or cortex, which entirely surrounds its hemispheres except at their points of union. Owing to the peculiar formation of the brain into convolutions or gyri, which form more or less deep infolds or fissures, the deepest of which serve to divide the brain into lobes, only about one-third of the cortex appears externally. The thickness of the cortex varies at different locations and points, ranging from 1.5 to 4 mm. Toward the front of the brain, and especially at the summit of the pre-central convolution, in what are commonly known as the sensory-motor areas, the cortex is not only the thickest, but its cells are the largest, while in the visual areas at the back of the brain the cortex is the thinnest while it is also the densest.1

While minute but very elastic blood-vessels and

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