Diseases of the nervous system / edited by Archibald Church.

Date:: 1908

Credit: Diseases of the nervous system / edited by Archibald Church. Source: Wellcome Collection.

33/1256 page 5

$tively late, there is no absolute parallel between the mental development of the animal and the formation of fossae in the cerebrum. We know that some animals have perfectly flat brains and that in others the brain is markedly convoluted, yet we are unable to determine a preponderance of cerebral activ- ity in the latter. Of course, in the highest group of mammals, monkeys, from the lowest forms up to the anthropomorphic apes, there is an increasingly rich for- mation of fossae and convolutions which finally reaches its acme in the human brain. The importance of the fossae unquestionably depends upon the greatest possible surface distribu- tion of the cortex of the cerebrum within the limited space of the cavity of the skull. Although the ganglion cells of the cortex constantly increase in numbers by the development of the brain, and space is formed by their over- lapping each other in layers, the thickness of the cortex thus being permanently increased, a juxtapo- sition of the nervous elements is of great importance, above all for the development of the projection fiber systems which unite the cor- tex of the brain with the deeper portions of this structure. Since, as Bail- larger pointed out, when the brain begins to grow its volume forms the cube of its diameter while the surface equals only the square of its diameter, many convolutions must develop in the surface in order to preserve this ratio between volume and diameter. At this point it may be interesting to discuss the question in how far in man the weight of the brain and its richness in convolutions may presage his mental development. In beginning our investigations into the brain we incline to the general opinion that great weight of the brain is combined with a great intellect. Numerous measurements made for this purpose among various races and also measurements in the case of noted men have proven that there is for this no absolute rule, but that while the brains of some prominent men were very large, others did not exceed the average or were even below it. The fact that the brain in men is, upon the average, heavier than in women, and that in various races the weight of the brain does not markedly differ, may be attributed almost wholly to the difference in the general size and weight of the body, with which the weight of the brain appears to correspond. A little reflection will also show that the nervous elements in the cortex of the brain which mold our psychical life determine also the weight of the brain rather than the basic substance of the brain, JS T Fig. 4.—Brain of a Human Fetus at Seven Months. A, Fiss. Sylvii; h, gyr. central, ant.; I2, gyr. front, sup.; h, gyr. front, med.; /*, gyr. front, inf.; II\, gyr. central, post.; 112, lob. parietal sup.; II3, lob. parietal, inf.; III 1, gyr. occ. sup.; III2, gyr. occ. med.; Ilh, gyr. occ. inf.; IV\, gyr. temp, sup.; IV2, u.3, gyr. temp. med. u. inf.; V, insula; B, fiss. parieto-occip., lateral portion; E, sulc. cen- tralis; P and P, anterior and posterior portions of the sulc. interparietalis; Pi, sulc. postcentralis; T, sulc. temporalis sup.$

Diseases of the nervous system / edited by Archibald Church.

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