To quote from my book, MENTALITY: “Con­stant exercising of the mental functions in constructiveness creates expansion of those organs which develops greater efficiency for absorbing it.
 “The chief governing functions of the mental system are located in the brain which is a mass of cells and tissue that almost fills the cavity inside of the skull. It has three parts—cerebrum, cerebellum and medula oblongata—each of which has separate governing functions.
 “The weight of the brain of an adult will average about three pounds. Its weight and size is increased by concentrated thinking. It obtains its fuel for power from substances brought to it by the blood.
 “The brain is made of two kinds of materials — gray matter composed largely of cells that are operated by the menorgs and white matter consisting principally of fibers through which the currents of mentality pass to all parts of the body.
 “The cerebrum, in which the mind is located, is in the top-most and largest part of the brain. It is covered with deep furrows and convolutions and is divided into two parts by a groove extending from front to rear. The right half controls the left side of the body and the left half, controls the right side of the body.
 “The cerebellum, in which the muscle centrol is centered, lies at the back of the nead beneath the cerebrum.
 “The medula oblongata is situated between the main brain and spinal cord. It is about one and a quarter inches in length and controls the heart action, breathing, swallowing and the expansion and contraction of the blood vessels of the vaso-motor system.
 “Connecting with the medula oblongata and running downward inside of the spinal column is a circular cord about a half-inch in diameter known as the spinal cord which terminates at the lower end of the backbone.
 “There are two mental channels—sensory and motory.
 “The sensory channel carries from all parts of the body to the mental centers and brain the impressions felt by the skin, tongue, nostrils, eyes and ears.
 “The motory channel conveys the orders issued from the brain through the mental centers to the different muscles of the body.
 “One channel is used by the brain for receiving messages and the other channel is used by the brain for sending messages.
 “Each channel from the spinal cord starts from the cells in the center of the cord and passes between the vertebrae and outward to the different parts of the body connecting with the brain. Each of these channels comes from the cord in the two branches known as roots.
 “The anterior root conveys orders from the brain to the muscles and the posterior root carries the impressions from the skin and