196   Tablets  Contains  Salol  and  Quinine  Sulphate.  { Am-M°ayr"  f9hia7rm' 
is  immersed,  surrounded  by  a  water  bath  kept  warm  by  an  immersed, 
painted-black,  carbon  lamp.  From  an  elevated  container  Locke's 
solution  is  passed  down  through  a  coil  in  the  water  bath  (thereby 
warming  it  as  needed)  and  up  into  the  amber  chamber,  filling  the 
chamber  from  the  bottom,  at  which  place  there  is  also  an  outlet. 
Warmed  air  (warmed  by  passing  through  another  coil  in  the  bath) 
is  made  to  gently  bubble  through  the  Locke's  solution,  thereby  keep- 
ing it  aerated  and  circulating.  The  water  in  the  outer  bath  is  also 
kept  circulating  by  a  current  of  air  in  order  to  maintain  an  even 
temperature  throughout  the  bath.  The  amber  chamber  bears  a  cork 
stopper  at  the  top  carrying  a  thermometer,  and  the  tube  conveying 
the  air  and  to  which  the  uterus  is  attached.  The  stopper  has  two 
holes,  one  for  the  thread  to  the  writing  lever,  and  one  through  which 
to  inject  the  pituitary  solution.  In  this  all-glass  apparatus  light  is 
practically  excluded  from  the  uterus,  except  for  that  which  passes 
through  the  amber  glass,  and  at  the  same  time  all  the  contents  may 
be  readily  observed,  rendering  easier  the  control  of  dilutions,  tem- 
perature, emptying  of  the  chamber,  rate  of  air  flow,  and  so  on. 
Material. 
The  uteri  of  virgin  guinea  pigs  weighing  from  175  to  250  grams 
have  been  commonly  used.  Larger  pigs,  up  to  300  grams,  have 
usually  furnished  less  satisfactory  uteri. 
Method  and  Procedure. 
The  animal  is  killed  by  instantaneous  decapitation.  The  whole 
uterus,  with  a  small  section  of  vagina  but  without  ovaries,  is  removed 
and  placed  in  a  fold  of  cotton  saturated  with  warm  Locke's  solution 
until  a  horn  can  be  separated,  attached  to  the  tube,  and  placed  in 
the  chamber. .  The  vaginal  end  of  the  horn  is  tied  to  a  little  post  on 
the  air  tube  by  means  of  a  silk  thread,  which  is  sewn  into  the  peri- 
toneal covering  on  the  side  of  the  broad  ligament.  The  ovarian 
end  of  the  horn  is  attached  to  the  thread  running  to  the  writing 
lever  by  a  small  pin  hook  which  is  passed  through  the  Fallopian 
tube,  or,  if  the  horn  is  unusually  long,  a  part  of  the  ovarian  end  is 
removed  and  the  hook  is  passed  through  the  peritoneal  fold  as  be- 
fore. The  tube  bearing  the  uterus  is  then  placed  in  the  chamber, 
the  thread  attached  to  the  writing  lever,  the  uterus  weighted  down 
with  from  1  to  4  grams  (usually  iT/2  to  3),  the  writing  lever  brought 
