Page:Popular Science Monthly Volume 76.djvu/438

434 early stages of the malady the same cause leads, no doubt, to reflex derangement of the secretion of the stomach involving nausea. Disturbances of vision add to the victim's discomposure, and in some small degree precipitate the stomachic catastrophe; but the effective cause is, I take it, the agitation, by impulses from the semicircular canals, of the gray matter of the hind-brain.

Hiccough, again, is an exaggerated reflex due to increased conductivity of gray matter. A child takes a cold drink, or he rapidly fills his stomach with insufficiently masticated food. The ends of the vagal nerve in the stomach are irritated. They convey an influence which sets up the pain-condition in a portion of the gray matter through which nerve-fibers from the lungs extend their roots towards the nucleus of the phrenic nerve. The diaphragm sneezes.

It would carry us beyond the proper sphere of this journal were we to consider the phenomena of inhibition of some reflexes and exaggeration of others which the modification of the normal conductivity of gray matter due to the establishment of pain-conditioned foci, brings about in hysteria, angina pectoris and many other morbid conditions.

The pain of headache is as truly "referred" as is the pain of angina pectoris, although it must be assigned to a different category. Medical men tell their patients that their headaches are in their scalps and not within their skulls. The patient finds it difficult to understand how this can be, when there is nothing the matter with his scalp; but agrees with his doctor that, were it otherwise, it would be impossible to explain the beneficial effect of a cold wet rag. Again as in sea-sickness the vagal nerve is at the bottom of the mischief. Indeed, in many persons, intolerable headache takes the place of sickness on the sea. Impulses ascending the vagus agitate the gray matter of the hind-brain. Into this pain-conditioned gray matter the nerves of the scalp pour a constant stream of impulses. Myriads of fibers connecting the scalp with the brain twang ceaselessly with messages to which, under normal circumstances, consciousness gives no heed—until a draught of cold air or the tickling of a fly's feet accentuates a certain group. Let the gray matter through which they pass be pain-conditioned, the vibrations traveling to the cortex from innumerable spots on the surface of the head produce a widely diffused dull ache which has no sensational quality, because no particular group of nerve-endings is being especially stimulated by external force. Vascular changes in the scalp due to the same cause, the exaggeration of impulses during their transit of the gray matter of the hind-brain, making believe that the scalp is injured and needs more blood, react upon the nerve-endings increasing the illusion of injury. The pain is no illusion. It is impossible to decide whether vascular changes are the first effect of vagal agitation and therefore the immediate cause of pain or whether they are merely subsidiary results of the exaggeration of sensory impulses from