Definition of "brain" []

• The portion of the vertebrate central nervous system that is enclosed within the cranium, continuous with the spinal cord, and composed of gray matter and white matter. It is the primary center for the regulation and control of bodily activities, receiving and interpreting sensory impulses, and transmitting information to the muscles and body organs. It is also the seat of consciousness, thought, memory, and emotion. (noun)
• A functionally similar portion of the invertebrate nervous system. (noun)
• Intellectual ability; mind: a dull brain; a quick brain. (noun)
• Intellectual power; intelligence. Often used in the plural: has brains and good looks. See Synonyms at mind. (noun)
• A highly intelligent person. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "As to the divisions of the greater brain or cerebrum, we want you to note that the _lower brain_ serves a double purpose."
• "Instantly the tiny nerve bulbs in the skin of the sole of your foot are stimulated, or set in vibration, and they send these vibrations up the sciatic nerve, into and up the whole length of the spinal cord, through the medulla, which switches them over to the other side of the brain up through the _brain stalk_, and out to the part of the surface (cortex) of the brain which controls the movements of the foot."
• ""I think I can answer this question in a satisfactory manner, difficult though it seems; but in order that I may do so, I would ask the reader to lend me his attention for a few moments while we regard the brain simply _as brain_, and have no other idea concerning it than we can derive from inspection and reflection."