432 THE POPULAR SCIENCE MONTHLY 



to ascertain whether it was hot. It was a frosty morning in November. 

 Obviously, the stranger had a strong prejudice that the station-master 

 would not have thought it necessary to order a tire to be lighted so 

 early in the winter. As nearly as I could estimate, three seconds 

 elapsed between the touching of the stove and the ejaculation which 

 announced with unnecessary emphasis that the man had obtained the 

 information he desired. Had he, expecting to find the iron hot, directed 

 his attention to the modification of his skin sensation he would have 

 withdrawn his fingers in one seventh of a second. 



One of the characteristics of incipient pain is exaltation of reflex 

 actions. I can not by any effort of will prevent my muscles from with- 

 drawing my hand from hot iron (although the resolute withdrawal of 

 attention from pain-modified sensations and the forcing of a conviction 

 that it does not exist, has in certain cases a remarkable effect in sup- 

 pressing pain). Equally characteristic of established pain is the inhibi- 

 tion of action. A whitlow abolishes all temptation to shake the finger. 



Physiologists can not investigate the phenomena of pain, although 

 they make elaborate studies of its threshold value and of the distribu- 

 tion of " pain spots." It would take us too far were we to consider the 

 evidence of a degree of specialization in the protopathic nerves of the 

 skin which is held by some to justify the use of the expression " pain- 

 nerves," and of the allied question of neuronic conduction of incipient 

 or threshold pain along pain-tracts in the spinal cord. 



The chief interest of the hypothesis of structural continuity through 

 the protopathic nervous system, with its corollary of sympathetic nu- 

 tritional change, lies in the explanation which it affords of the influ- 

 ence upon reflex action of the establishment of a pain-condition in the 

 axial nervous system in circumstances in which, consciousness not 

 being affected, there is no " pain." 



Pain-condition which inhibits reflexes due to impulses which start 

 in the damaged organ or skin area, greatly increases in many in- 

 stances the conductivity of the portion of the nervous system which it 

 affects for impulses which do not come from the damaged part. Such 

 a reinforced reflex is the attack of sneezing to which many persons, 

 most monkeys, and some breeds of dogs are subjected when the eye is 

 stimulated by a bright light. When the gaze is directed towards a 

 bright cloud, excessive stimulation of the retina sets up a pain-condition 

 in the mid-brain. In the progress of evolution this portion of the 

 cerebrospinal axis has undergone great changes. Its sensory nerves 

 with their protopathic constituents have been drawn backwards into 

 the great bundle of the fifth nerve, which joins the hind-brain, whilst 

 the nerve from the retina has established a secondary connection with 

 the mid-brain. The mid-brain receives in consequence the protopathic 

 nerves of the eye. But the nose being the real tip of the body and 

 anterior to the eye the sensory fibers of the skin which lines it al- 



