Journal of comparative neurology . ealed. Great care was taken to remove all of thecells of the cerebral hemisphere in all the operations. The above experiments subject the brain tissue left by theextirpation of the hemisphere to two conditions. In the firstseries of operations the nervous tissue is left to regenerate with-out the possibility of any stimulus from the end organ that isnormally connected with it. In the second series the end organ,the nasal placode, is left in its normal position and may there-fore act as a stimulus to the nervous tissue (Burr 16). In the first series of experim
Journal of comparative neurology . ealed. Great care was taken to remove all of thecells of the cerebral hemisphere in all the operations. The above experiments subject the brain tissue left by theextirpation of the hemisphere to two conditions. In the firstseries of operations the nervous tissue is left to regenerate with-out the possibility of any stimulus from the end organ that isnormally connected with it. In the second series the end organ,the nasal placode, is left in its normal position and may there-fore act as a stimulus to the nervous tissue (Burr 16). In the first series of experiments in which the right hemisphereand the right nasal placode were removed the wound usually BRAIN REGENERATION IN AMBLYSTOMA 205 healed within the first twenty-four hours. Five days after theoperation a new wall had formed connecting the wall of theright diencephalon with the wall of the left telencephalon. Atfirst this wall consists of a nariow band of new cells bridgingthe interventricular foramen. As growth proceeds the narrow. Fifl. 1 Transverse section of embryo five days after operation, hy whichthe cerebral hemisphere was removed, leaving the nasal placode in place, .-^how-inp: curtain of cells across the interventricular foramen. X 50. band of cells is drawn (nit into a thin plate, never more than twoor three cells thick, stretching across the foramen (figs. 1 and 3).A careful inspection of a series of operated larvae makes it(juite clear that the new tissue thus formed is derived from theprimary ependymal cells that line the neural tube. Figure 2dra^^^l from a section of an operated larva of the second seriesshows the origin of this new tissue from the margin of the dien- 2()() H. SAXTON liVlUi ((>))lial()ii. It is (()inj)()S((l (Mitirclx of tlic ty])ic;il colutuiiaicells thai make u]) the opeiulyiiui. As j»;r()vvth ])r()ceeds thecells of the lunv nieiiil)nine lose their coluiiniar shape and be-come metainor])hose(l into flattened quadrilateral cells. In thethree
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Keywords: ., bookauthorw, bookcentury1900, bookdecade1910, booksubjectmedicine
