The human brain is an elaborate organ, exceedingly complicated in its convolutions. We can not, indeed, describe it as the most convoluted, for the brain of the elephant is at least as distinguished for the beauty and complication of its folding, and the brain of the whale is far more minute and detailed, presenting quite a multitude of minute convolutions. For descriptive purposes, the human brain is divided into four superficial areas, known as lobes, and pretty clearly defined by certain natural boundaries. From the lower part of the organ, entering at a point scarcely half way back is a fissure or cutting running up into the mass in a direction uniformly inclining towards the rear, known as the Sylvian fissure; while coming over the summit, at a point near the middle, and inclining down towards that just described, is another fissure, known as the fissure of Rolando. By these two deeply cut hollows, the brain is marked off into four separate areas superficially, a front and a rear lobe; and two central lobes, the one upper and the other under. Besides this there is a concealed and isolated lobe, described on account of its situation as an island, which is covered from view by the overlapping of the two sides of the Sylvian fissure. Such is a description in outline of the configuration of the human brain, to which must be added the statement that each lobe is filled in with its own special arrangement of convolutions, each one having at least three well defined lines of convolution. Each of the hemispheres is similarly arranged, though not by any means quite identical in disposal of convolutions, yet the general description now given is strictly applicable to both. The two hemispheres, connected mainly with the ramification of nerve fibre running to the opposite sides of the body, are united together a considerable way down by a transverse band of nerve fibres, which at once unite the two into one organ, and make the union so effected a living efficient union by carrying a multitude of lines of communication from the one side to the other. Just below this, in the interior of the organ are two great central bodies, known as the basal ganglia, and consisting of nerve fibres massed together with grey matter around them, that in front being chiefly motor nerves brought to a junction, the latter sensory nerves combined in like manner. The same arrangement holds in both hemispheres, thereby providing that the respective masses of motor, and of sensory nerves lie exactly opposite each other. Behind these in the centre, lying in a position under both hemispheres are four small bulbs connected with the nerves of vision, and also with the cerebellum; and behind them, covered by the posterior lobe of the brain is the cerebellum itself, or little brain, largely concerned with coördination of movements, or equilibrium of the two sides of the system. Just below these arrangements the two