The state set up in the segment of the cord in which afferent fibres, conveying pain from viscera, embouch affects its conductivity. It subdues reflex action through the segment, and at the same time facilitates or reinforces the transmission of sensory impulses towards the seat of consciousness. This shows itself in the apparent increased sensitiveness of the skin of the area of the surface supplied by the posterior root which joins the segment of the spinal cord into which the pain influence is also being poured. For example, afferent sympathetic nerves from the cardiac end of the stomach join the sixth and seventh thoracic spinal nerves. Other afferent fibres run up the vagus to the medulla oblongata. When the cardiac end of the stomach is diseased, pain is referred to the skin area supplied by the sixth and seventh dorsal roots. The ordinary inevitable stimuli acting upon this area cause pain. Experimental stimuli which elsewhere would be felt as touch or warmth are painful. The impulses to which they give rise pass through pain-agitated segments of the spinal cord. The vagus nerve carries its pain influence to the medulla oblongata. Now, it happens that the sensory nerve of the face—the fifth—spreads for a considerable distance up and down the axis of the brain. The fifth nerve in consequence pours its sensory impulses into a region which is pain-agitated by those fibres of the vagus which come from the cardiac end of the stomach. Hence disease of that organ gives rise also to an “illusion” of pain—pains and illusions of pain are philosophically indistinguishable—on the surface of the head. The viscera, having no direct access to consciousness, appear by deputy. When the stomach is distressed, it makes its appeal to the whole body politic for considerate treatment through certain nerves which have the privilege of appearing at Court. The message is misread as coming from the front of the chest—“heart-burn”—or from the shoulder, or from the scalp, or from the other skin areas which these nerves serve. When the liver is in trouble, consciousness, having no knowledge of its whereabouts—is it the business of hand and eye to explore another man’s liver, or incumbent upon the mind to accept their findings?—infers that the cry comes from the shoulder. Nor have the tissues beneath the root of the nail, or the muscle of the shoulder, or the pulp of a tooth, any direct representation in consciousness; but since the pain-condition in the grey matter converts it into a microphone, messages from neighbouring structures which otherwise would fail to arouse attention, after traversing the pain-segments of the nervous system, ring out clearly, and hence the mind locates approximately the “pain” of the whitlow, the muscle-ache, the decayed tooth. Sufferers from toothache are familiar with the phenomenon of the spread of pain from a definite spot to the whole jaw or the whole side of the head, dependent upon the spread