All the psychic activities of the brute, such as sensation, object-perception, imagination, associative memory, sensual emotion, etc., are organic functions of the sensitivo-nervous type. In all of them the agent and recipient is not the soul alone, but the psycho-organic composite of soul and organism, that is, the soul-informed sensory and central neurons of the cerebrospinal system. The sensory neurons are nerve cells that transmit centerward the excitations of physical stimuli received by the external sense organs or receptors, in which their axon-fibers terminate. These receptors and sensory neurons are extended material organs proportioned and specialized for receiving physical impressions from external bodies, either directly through surface-contact with the bodies themselves or their derivative particles (_e.g._ in touch, taste and smell), or indirectly through surface-contact with an extended vibrant medium such as air, water, or ether (_e.g._ in hearing and sight). The central neurons of the cerebral cortex are, as it were, the tablets, upon which the excitations transmitted thither by the sensory neurons, record the extended neurograms that constitute the physical basis of the concrete imagery of memory and imagination. Interior senses, then, like memory and imagination, merely continue and combine what was preëxistent in the exterior senses. Their composite imagery is rigidly proportioned to the extended neurograms imprinted on the cerebral neurons, and these neurograms, in turn, are determined both qualitatively and quantitatively by the physical impressions received by the receptors, and these impressions, finally, are exactly proportioned to the action of the material stimuli in contact with the receptors. Thus the composite images of imagination as well as those of direct perception are proportioned to the underlying neurograms of the cortex and correspond exactly, as regards quality, intensity, and extensity, to the original stimulus affecting the external receptors. Hence men born blind can never imagine color, nor can men born deaf ever imagine sound. An inextended principle, such as the discarnate soul, cannot receive or record impressions from extended vibrant media, or from extended corporeal masses. For this the soul requires the intrinsic coöperation of material receptors. Now, the highest cognitive and appetitive functions of the brute (_e.g._ sense-perception and emotion) are, as has been stated, of the sensitivo-nervous or psycho-organic type, that is, they are functions in which the material organism intimately coöperates; brute animals give no indication of having so much as a single function, which proceeds from the soul alone and which is not communicated to the organism. Hence the bestial soul is “totally immersed” in matter; as regards both operation and existence, it is “intrinsically dependent” upon its material complement, the organism. It never operates save in conjunction with the latter, and