Again, functional analysis generally remains very rudimentary and limited to the needs of the clinic; while the great majority of the available anatomical examinations are also very inadequate. Localizations have been established according to the morphology of the convolutions, which: have no necessary connection with the functional areas: they correspond to the cell structures which the cyto-architectonic of the brain has begun to establish, and which often cover different convol u tions,
Another new difficulty lies in the individual variability which is possible in psycho-physical mechanisms, and which is beyond doubt constitutional: cerebrally rightand left-handed individuals provide an obvious example of this. The cyto-architectonic shows that the relations of functional areas with a morphological appearance vary greatly with the individual, so that any judgment based on the appearance of the convolutions-which are already so variable-is suspect. Finally Moutier has emphasized the extraordinary variability of arterial distribution, of the vascular divisions and channels, in particular in the area of the fissure of Sylvius, which results in great differences in the complexity of lesions for an arterial embolus of a given trunk, according to the topographical type.