413


time  natural,  inspirations,  one  of  the  valves  of  the  inhaler  permitting
the  exhalations  to  pass  off.
Fio.  165.
After  thus  inhaling  the  gas  for  a  few  minutes,  its  ansesthetic  effects
are  shown  by  strong  involuntary  respirations  attended  by  a  snoring
sound,  owing  to  the  relaxation  of  the  muscles  of  the  pharynx.  Then
follows  a  livid  appearance  of  the  lips,  from  the  discolored  blood  in  the
capillaries.  A  spasmodic  twitching  of  the  muscles  is  observed  at  this
stage  in  many  patients,  when  complete  narcosis  follows.  The  narcotic
effects  of  the  gas  continue  from  thirty  seconds  to  one  and  a  half  minutes,


414  USE    OF    ANESTHETIC    AGENTS.
and  the  number  of  teeth  which  can  be  extracted  varies  from  four  to
twelve.  It  is  no  unusual  occurrence,  however,  for  the  extraction  of
one  tooth  to  consume  the  entire  time  the  patient  is  under  the  narcotic
influence  of  the  gas,  while,  in  other  cases,  more  than  the  highest  number
just  mentioned  may  be  removed  before  the  patient  becomes  conscious
to  pain.  Nitrous  oxide  gas  is  considered  to  be  the  safest  general  anes-
thetic now  in  use,  and  does  not  produce  the  nauseating  and  debilita-
ting effects  which  are  often  caused  by  ether  and  chloroform.  Ex-
treme caution,  however,  is  necessary  in  administering  this  gas  under
circumstances  which  prohibit  the  use  of  other  general  ansesthetic
agents.  The  greatest  objection  to  its  use,  aside  from  the  question  of
safety,  is  the  rapidity  in  operating  which  its  transient  eflTect  necessitates ;
and  it  is  much  better  to  carefully  extract  a  few  teeth  than  to  attempt
the  removal  of  many  by  an  operation  which  may  be  attended  with
severe  laceration  of  the  gums  and  fracture  of  the  alveolus.
