BRAIN n.
It is simply the anterior termination of the spinal cord, and is developed from three embryonic vesicles, whose cavities are connected with the central canal of the cord; the cavities of the vesicles become the central cavities, or ventricles, and the walls thicken unequally and become the three segments, the fore-, mi…
CHALK n.
sion, a compound, as of clay and black lead, or the like, used in the same manner. See Crayon. Black chalk, a mineral of a bluish color, of a slaty texture, and soiling the fingers when handled; a variety of argillaceous slate. -- By a long chalk, by a long way; by many degrees. [Slang] Lowell. -- Chalk drawing (Fine…