. A treatise on nervous and mental diseases, for students and practitioners of medicine. Laminated cortex from the brain of a rabbit. (Bevan Lkwis.) ANATOMY. 31 Thus the granule cell predominates in both toward the occipitallobe, and the five-laminated type is especially developed toward thefrontal lobe. There are also striking divergences between the mam-malian and human brain; so that in the rodent, for instance, thetransition from the one type of cortex to another is very abrupt,whilst in the human brain these types fade into one another sogradually that it is scarcely possible to draw the
. A treatise on nervous and mental diseases, for students and practitioners of medicine. Laminated cortex from the brain of a rabbit. (Bevan Lkwis.) ANATOMY. 31 Thus the granule cell predominates in both toward the occipitallobe, and the five-laminated type is especially developed toward thefrontal lobe. There are also striking divergences between the mam-malian and human brain; so that in the rodent, for instance, thetransition from the one type of cortex to another is very abrupt,whilst in the human brain these types fade into one another sogradually that it is scarcely possible to draw the line of demarcation,the five-laminated cortex of the human motor area shading graduallyinto the six-laminated cortex external and posterior to it. In therodent, too, the motor area or ganglionic cells, which are to be seenin the fourth layer in the human cortex, are spread over a far greaterproportionate surface of the hemisphere, whilst in the human beingthey are limited to certain small regions, as shown in Fig. 12. Fig. 12. R-. Left ascending frontal and parietal gyri, with the attached frontal convolutions, as seen at the First group of ganglionic cells. E-G. Second group of ganglionic cells. H, group of ganglionic cells. M, N. Barren area. N, 0. Fourth group of ganglioniccells. Fb. Eegion of large elongate cells. Fig. 12 is the result of an investigation of these motor areas in eighthuman brains, made in 1878 by Bsvan Lewis and Dr. Henry upper group (A-D) represents the largest cells and the mostperfect and dense clusters. These ganglionic cells are, as shown byBetz, who called them the giant pyramids, generally arranged inclusters or nests. Betz first suggested their probable motor believes that the large size of these cells is due to the dis-tance which their apex process has to transverse in attaining theouter layer of the cortex; but Bevan Lewis has shown that evenlarger cells are found nearer the upper surface of the cort
Size: 1842px × 1357px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1890, bookidtreatiseonnervou00gray
