700 
ME.  J.  LISTEE  ON  THE  EAELT  STAGES  OF  ENTLAIMMATION. 
by  the  results  of  this  investigation  is,  that  it  is  necessary  to  draw  a broad  line  of  demar- 
cation between  inflammation  produced  by  direct  irritation,  and  that  which  is  developed 
indirectly  through  the  medium  of  the  nervous  system,  whether  in  the  immediate  vicinity 
of  a source  of  irritation,  as  around  a tight  stitch  in  the  skin,  or  a thorn  in  the  finger, 
or  at  a distance  from  the  disturbing  cause,  as  when  the  kidneys  are  affected  in  conse- 
quence of  the  passing  of  a bougie,  or  the  lungs  through  exposure  of  the  feet  to  cold. 
Nothing  can  better  illustrate  the  importance  of  this  distinction,  than  what  takes  place  in 
a recent  wound.  In  consequence  of  the  injury  iaflicted  hy  the  knife,  together  with  the 
subsequent  manipulation  and  exposure,  the  tissues,  in  a thin  layer  at  the  cut  surface,  are 
thrown  into  that  condition  which  leads  to  effusion  of  liquor  sanguinis,  the  fibrine  of  which, 
speedily  coagulating,  remains  to  constitute  the  bond  of  primary  union,  while  the  serum 
trickling  away  between  the  lips  of  the  wound  produces  the  discharge  which  soaks  the 
dressing  during  the  first  twenty-four  hours.  But  neither  during  the  exudation  of  the 
lymph  in  such  a case,  nor  during  its  subsequent  organization,  is  there  necessarily  any 
inflammation  induced  in  the  lips  of  the  wound  through  the  neiTous  system ; and  if  this 
complication  does  occur,  it  interferes  with  the  healing  process  in  a degi’ee  proportioned 
to  its  intensity.  In  other  words,  while  a certain  amount  of  inflammation  as  caused  by 
direct  irritation  is  essential  to  primary  union,  any  degree  of  it  as  induced  indii’ectly  is 
both  unnecessary  and  injurious. 
The  question  how  inflammation  is  developed  through  the  medium  of  the  nervous 
system,  possesses  a high  degree  of  interest,  in  consequence  of  its  bearing  upon  the  manner 
in  which  counter-irritation  operates  therapeutically.  In  the  integument,  where  we  have 
the  opportunity  of  seeing  the  affected  part,  the  first  indication  of  the  supeiwention  of 
inflammatory  disorder  around  a centre  of  irritation  is  a blush  of  redness,  which,  as 
before  shown  *,  consists,  in  the  first  instance,  of  mere  dilatation  of  the  arteries  with  rapid 
flow  of  blood  through  the  capillaries.  It  is  quite  conceivable  that  arterial  dilatation, 
carried  to  an  extreme  degree  along  with  powerful  action  of  the  heart  f,  may  so  increase 
the  tension  upon  the  tissues  as  to  impan  their  powers  gradually  by  mechanical  irri- 
tation, just  as  the  frontal  integument  is  affected  by  long-continued  gentle  pressme  from 
without,  as  above  alluded  to ; for  we  know  that  when  inflammation  does  exist,  mere 
increase  of  tension  upon  the  blood  in  the  vessels  will  greatly  aggravate  the  disorder,  as 
when  an  inflamed  foot  is  kept  in  a dependent  posture.  Supposing  this  to  be  the  whole 
mechanism  of  the  disease,  its  origin  would  be  sufficiently  mteUigible ; for  we  have 
seen  that  vascular  dilatation  caused  by  irritation  operating  through  the  medium  of  the 
nervous  system  appears  to  depend  on  a depressing  influence  produced  by  excessive  action 
of  the  afferent  nerves  upon  the  ganglia  which  preside  over  the  arterial  contractions. 
There  are,  however,  some  circumstances,  such  as  the  di’yness  of  the  nostril  which  may 
exist  in  the  early  stages  of  coryza,  and  sudden  suppression  of  mine  in  consequence  of 
* See  page  665. 
t It  is  to  be  observed,  that  in  the  frog,  when  fuU  dilatation  of  the  arteries  lasts  for  days  together  without 
the  production  of  inflammatory  congestion,  the  state  of  the  vessels  has  been  brought  about  by  a very  serious 
operation  which  greatly  weakens  the  action  of  the  heart. 
