. Anatomy, descriptive and applied. Anatomy. 962 THE NERVE SYSTEM But this development of mature nerve fibres does not occur simultaneously throughout the brain, but step by step in a definite order of succession; equally important bundles are myelinated simultaneously, but those of dissimilar importance develop one after another in accordance with Flechsig's law. The successive myelinization of fibre bundles to and from the cerebral cortex corresponds to the successive awakenings of mental activities and faculties in the growing child. Flechsig's method of investigation has been of great serv
. Anatomy, descriptive and applied. Anatomy. 962 THE NERVE SYSTEM But this development of mature nerve fibres does not occur simultaneously throughout the brain, but step by step in a definite order of succession; equally important bundles are myelinated simultaneously, but those of dissimilar importance develop one after another in accordance with Flechsig's law. The successive myelinization of fibre bundles to and from the cerebral cortex corresponds to the successive awakenings of mental activities and faculties in the growing child. Flechsig's method of investigation has been of great service in the elucidation of the problems of cerebral localization. Craniocerebral Topography.—The position of the principal fissures and convolutions of the cerebrum and their relation to the outer surface of the scalp (Fig. 677) have been the subject of much investigation, and many systems have been devised by which one may localize these parts from an exploration of the external surface of the head. These plans can only be regarded as approximately correct for several reasons; in the first place, because the relations of the convolutions and fissures to the surface are found to be quite. Fig. 722.—Drawing to illustrate ] topography. (Taken from a cast in the Museu College of Surgeons of Kngland, prepared by Professor Cunningham.) I of the Royal variable in different individuals; secondly, because the surface area of the scalp is greater than the surface area of the brain, so that lines drawn on the one cannot correspond exactly to fissures or convolutions on the other; thirdly, because the fissures and convolutions in two individuals are never precisely alike. Nevertheless, the principal fissures and convolutions can be mapped out with sufficient accuracy for all practical purposes, so that any particular convolution can be generally exposed by removing with the trephine, or by the flap method, a certain portion of the skull. An excellent method is given by
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