If the reader has not fully mastered the intricacy of the brain structure, he will find his difficulties removed by studying two more skilful dissections. The following engraving presents the appearances when we cut through the middle of the brain horizontally and reveal the bottom of the ventricles, in which we see the great ganglion, or optic thalamus and corpus striatum, and the three localities at which the hemispheres are connected by fibres on the median line, called anterior, middle, and posterior commissures. These commissures are of no importance in our study; they assist the corpus callosum in maintaining a close connection between the right and left hemispheres. [Illustration] Behind the thalami we see the quadrigemina, the posterior pair of which is labelled _testes_, and resting upon them we have the pineal gland, a centre of spiritual influx. Behind the thalami, the posterior lobes are cut away that we may look down to the cerebellum, and the middle of the cerebellum is also removed so that we may see the back of the medulla oblongata and its fibres, called restiform bodies, which give origin to the cerebellum. The fibres from the cerebellum to the quadrigemina are shown, and the space at the back of the medulla, called the fourth ventricle. As the fibres of the medulla pass up through the pons to the great inferior ganglion, and the fibres of the corpus striatum pass outward and upward to form the cerebrum, this procession of the fibres is shown in the annexed engraving, in which we see the restiform bodies passing up to form the cerebellum, and the remainder of the medulla fibres passing through the pons, and then, under the name crus cerebri or thigh of the cerebrum, passing through the thalamus and striatum to expand in the left hemisphere of the cerebrum. We see the quadrigemina on the back of the ascending fibres and their connection by fibres with the cerebellum behind, as they connect with the thalami in front. This is as complete a statement of the structure of the brain as is necessary, and further anatomical details would only embarrass the memory. [Illustration] The engraving above represents not an actual dissection, but the plan of the fibres as understood by the anatomist. The intricacy of the cerebral structure is so great that it would require a vast number of skilful dissections and engravings to make a correct portrait. Fortunately, this is not necessary for the general reader, who requires only to understand the position of the organs in the head, and the direction of their growth, which is in all cases directly outward from the central region or ventricles, so as to cause a prominence of the cranium--not a "bump," but a general fulness of contour. Bumps belong to the growth of bone--not that of the brain. Let us next consider the genesis of the brain, which will give us a more perfect understanding of its structure, by showing its origin, the correct method of estimating its development.