The brain is distinguished from all other organs by being the source of commands which all other organs obey, and being the immediate seat of the soul, which has no knowledge of anything occurring in the body, until a message or impression has reached it through nervous channels. The compression of all the nerves before they enter the cranium and connect with the brain would deprive us of all knowledge of the body, and of all sensations or perceptions; and the compression of the brain itself would render us totally unconscious, as if dead,--incapable of either thought or action. Manifestly, therefore, all the powers of the soul are lodged in and exercised through the brain; and as all distinct nerve structures have essentially different functions, and every different function requires a different structure, it is obvious that the vast variety of our psychic faculties, intellectual, emotional, sensitive, passional, and physiological, requires a corresponding multiplicity in the nervous apparatus; and this incalculably great multiplicity we find in the brain. The crude, mechanical idea that all the organs of the brain should be distinctly marked and separated by membranous walls or obvious changes of structure, is very unscientific; for even in the spinal cord, which is more easily studied, we do not find such separation between the widely distinct functions of sensibility and motility. Their nerve fibres run together undistinguished, and it is only by the study of pathological changes that we have been able to distinguish the course of the motor fibres, which to the most careful inspection are indistinguishable from the sensitive. Moreover, the functions of the brain are not like those of the spinal cord, of a widely distinct and opposite character in adjacent fibres, but exhibit a gradual variation, like the blending colors of the rainbow. The sensitive or psychic individual who touches any part of the head and feels an impression of the emotional, intellectual, or impulsive function in the subjacent convolution of the brain, will find the impression gradually changing as he moves his finger along the surface, until, after passing half around the cerebrum, he will feel an influence exactly opposite to that with which he started.