supplies the sensible imagery that undergoes the aforesaid process of analysis or abstraction. Such imagery, however, is a function of the cerebral cortex, and, for this reason, the normal exercise of the imagination presupposes the cerebral cortex in a normal physiological condition; and anything that disturbs this normal condition of the cortex will directly disturb the imagery of the imagination, and therefore indirectly impede the normal exercise of conceptual thought, which is abstracted from such imagery. Hence it is clear that the activity of both the intellect and the will is objectively dependent upon the organic activity of the imagination, and, in consequence, _indirectly_ dependent upon the physiological condition of the cerebral cortex, which is the organ of the imagination. Since, however, this dependence is objective rather than subjective, it does not, as we have seen, conflict with the spirituality of rational thought. The nature of conceptual thought is such as to exclude the participation of matter as a constituent of its specific agent and receptive subject. The objects of a cerebral sense like the imagination are endowed with extension, color, shape, volume, mass, temperature, and other physical properties, in virtue of which they can set up vibrations in an extended medium or modify an extended organ by immediate physical contact. But, while imagination makes us conscious of objects capable of stimulating extended material organs, the objects, of which we are conscious in abstract thinking, are divested of all the sensible properties, extension, and specific energies, which would enable them to modify a material neuron, or produce a physical impression upon a material receptor of any kind whatever. Between an extended material receptor, like a sense-organ or a cerebral neuron, and the nondimensional, dematerialized object or content of an abstract thought, like science, heroism, or morality, there is no conceivable proportion. How can a material organ be affected by what is supersensible, unextended, imponderable, invisible, intangible, and uncircumscribed by the limitations of space and time? Extended receptors are necessary for picking up the vibrations of a tridimensional medium (like air or ether), and they are, likewise, essential for the reception of impressions produced by surface-contact with an exterior corporeal mass. In short, sensory neurons are needed to receive and transmit inward the quantitative and measurable excitations of the material stimuli of the external world, and central neurons are required as tablets upon which these incoming excitations may imprint _extended neurograms_, that are proportionate in intensity and extensity to the external stimulus apprehended, and that underlie and determine the concrete imagery (of which they are the physical basis). But when it comes to perceiving and representing the _meaning_ of duty, truth, error, cause, effect, psychology, means, end, entity,