SNEEZING, SEA-SICKNESS, PAIN 43* 



terns of nerves which originate in organs in which their ends are so 

 modified and so enveloped as to render them sensitive in the highest 

 degree to one particular order of stimulus, whether of smell, sight, 

 taste, hearing, touch, heat, cold, pressure or traction, and inaccessible 

 to stimuli of every other class. These nerves, with the chains of 

 neurones which link them to the muscles, via the spinal cord and brain, 

 stand out as a pattern on the basal system, like the pattern formed of 

 thicker fibers and coarser knots on a sheet of lace. 



In a book recently published, " The Body at Work," I have en- 

 deavored to present a picture of the nervous system and its activities, 

 which, although not original in any of its details, is new in their group- 

 ing and in its comprehensiveness. It is based upon the teaching that 

 the two great functions of the nervous system, notwithstanding that 

 they grade one into the other, must, for purposes of analysis and de- 

 scription, be considered apart. By the basal system of protopathic 

 nerves all the cells of the body, with the exception of those of the con- 

 nective tissues, bones, tendons and so forth, are bound together into a 

 continuous inseparable whole. No change can occur in the nutritive 

 condition of any part of the skin or of an internal epithelium without 

 the induction of a nutritive change in the central nervous system and 

 thence, onward, in the plain muscle-fibers of arteries and other struc- 

 tures of the segment of the body in which the inducing change occurs. 

 As contrasted with the influence which spreads through this basal 

 system the " impulses " which travel up the nerves of special sense are 

 peculiar in kind or, at any rate, in intensity. In order that they may 

 overcome the resistance of a chain of neurones they have a certain 

 potential, and progress in pulsations or waves. 



Pain is explained as due to the setting up in a particular segment 

 of the axial nervous system of a focus " pain-conditioned " sympathet- 

 ically with the injured tissues. Consciousness of pain depends upon 

 the direction of attention to impulses which ascend through the pain- 

 conditioned segment from end-organs of nerves of special sense. If 

 the seat of injury be the skin it is through the specialized nerves of the 

 injured spot that modified impulses reach the cortex of the brain. If 

 the seat of injury be an internal organ no effect is produced in con- 

 sciousness until the pain agitation of the spinal cord has become suffi- 

 ciently intense, and sufficiently wide-spread, to modify impulses which 

 ascend to the cortex from skin areas of the segment in which the viscus 

 is situate. The pain in angina pectoris is felt on the left side of the 

 breast bone at its lower end. This shows that the nerves of the aorta 

 have their centers in the same region of the spinal cord as the cutaneous 

 nerves of this area on the surface of the chest. 



To give an illustration of the difference of mechanism of pain and 

 of sensation. In a railway station lavatory I recently observed a man 

 who absent-mindedly placed his fingers on a free-standing iron stove 



