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Injuries of nerves and their consequences - Reflex Sympathetic ...

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186<br />

.<br />

INJURIES<br />

OF NERVES.<br />

US, when chilled, far different results from those which it<br />

gave when thoroughly warmed.<br />

I am well satisfied that in some cases <strong>of</strong> nerve wounds<br />

causing atrophic contractions <strong>and</strong> malpositions, a part <strong>of</strong><br />

the dullness <strong>of</strong> sensation may be due to the constrained<br />

postures in which the members have been kept.<br />

How<br />

this sense may suffer from such causes is well illustrated<br />

by the double sensation which is felt when we examine<br />

with crossed fingers any round object, as a marble. Parts<br />

unused to act together are here forced to do so, <strong>and</strong> in<br />

consequence we have the sensation <strong>of</strong> two balls instead<br />

<strong>of</strong> one ;<br />

in other words, we have created what has been<br />

happily called by Pr<strong>of</strong>. Alex<strong>and</strong>er a tactile squint. In a<br />

note to the treatise so <strong>of</strong>ten referred to, this subject was<br />

further illustrated by a curious observation which I made<br />

at that time, <strong>and</strong> have since repeated. Let the observer<br />

put his h<strong>and</strong>s behind him, <strong>and</strong> let them be placed back to<br />

back. Then let him interlock his fingers irregularly,<br />

making the positions unusual, <strong>and</strong> keeping up mutual<br />

pressure among the parts so treated. After a few minutes,<br />

should some one touch lightly one <strong>of</strong> the fingers, the<br />

tap will be felt, but now <strong>and</strong> then the person examined<br />

will find a difficulty<br />

in stating which finger has been<br />

touched, <strong>and</strong> he will also discover how strong<br />

is the<br />

instinctive tendency to aid his tact-sense by movement,<br />

<strong>and</strong> how readily such movement supplies the required<br />

information.<br />

There is but one part <strong>of</strong> the skin which seems remark-<br />

*ably deficient in power to localize sensations. When, in<br />

examining the toes, especially in laboring people, we<br />

touch them in succession, the third toe is sometimes<br />

mistaken for the fourth, <strong>and</strong> this for the third ;<br />

more<br />

rarely the fourth is mistaken for the fifth, or little toe,<br />

but this is hardly ever taken for the fourth. My friend<br />

Dr. J. H. Hutchinson informs<br />

me that he has made the

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