n. A supposed point in or part of the brain where sensation resides or becomes manifest; the so-called “seat of the soul”; hence, the undetermined part of the nervous system in which molecular activity of certain kinds and certain grades of intensity immediately causes sensation; loosely, the brain, or the brain and spinal cord; especially, the gray matter of these organs, or any nervous ganglion regarded as a center of sensation. Also sensory, sensitory.n. In biology, the whole sensory apparatus of the body, or physical mechanism of sensation, including the skin and entire nervous system as well as the special sense-organs; all the parts, organs, and tissues of the body which are capable of receiving or transmitting impressions from without.