434 TEE POPULAR SCIENCE MONTHLY 



early stages of the malady the same cause leads, no doubt, to reflex 

 derangement of the secretion of the stomach involving nausea. Dis- 

 turbances 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 conduc- 

 tivity 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 exagge- 

 ration 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 under- 

 stand 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. In- 

 deed, 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 con- 

 necting 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-condi- 

 tioned, 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 im- 

 possible 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 



