These fibre constitute by far the greater part of the white centrum oval of the hemisphere. The total transverse section of the crus and the fibre masses from the thalamus and basilar ganglia, does not comprise more than one-third of the entire mass. In the lower animal this relation is different. The projecting fibres, such as those of crus and capsule and the great ganglia, are not as massive as in man, but they are nearly equal to, and in still lower forms exceed, those connecting the gyri with each other. Hence the chief point of contrast noted on examining a transverse frontal section through the cerebral hemisphere of a man and an ape consists in the mass of the centrum ovale of Vieussens. The whole substance in man actually appears hypertrophied when compared with that of lower animals. It is the associating fibres which mainly mediate that complex co-ordination of the separate units of thought and action which constitute the anatomical basis of the highest mental functions (Fig. 117). The study of the human mind does not resolve itself merely into an analysis of individual faculties such as simple perceptions and motor innervations, but above all requires the establishment of their synthesis into the complex abstractions on which the ego depends. [Illustration: FIG. 117.] Neither anatomic nor physiologic researches are calculated to demonstrate just what associating fasciculi or what groups of such fasciculi are subservient to any particular co-ordination. Where, for example, the cortical area for vision overlaps that of the centre for forearm and hand, the associating fasciculus underlying the debatable land is subservient to the co-ordinations employed in writing and drawing. In like manner a similar associating bond extending from the centre of auditory word symbols to that of the tongue and lip centres may be considered a chief factor mediating the speech co-ordinations. A child originally has no adequate notion of distance or perspective, but will, in the first week of life, grasp at objects fifty feet away. Its first ideas of space are gathered from its own skin sensations; it learns to distinguish between single impressions when touching foreign bodies, and associated double ones as when it touches a part of its own body. In great part this may even be accomplished by an active infant during the last months of utero-gestation; it has learned thus to separate the conception of its own body from the confused chaos which all impressions originally constitute to the infant; the next lesson is to learn that to reach certain objects it moves a certain distance, while others are immediately in reach. It then discovers, therefore, that the discrimination by the eye is possible, since intervening objects which it has learned to measure by its own body or bodily movements as a gauge permit an approximate judgment of distance, in aid of which comes experiment in the shape of time requirements, since