480  Cat  Method  for  Testing  Digitalis,  Etc.  {^""ucSei- im'"" 
of  ouabain  for  cats,  according  to  Dr.  Hatcher,  is  .0001  gramme  per 
kilogramme  of  body  weight,  the  theoretical  amount  of  solution  would 
be  the  number  of  cubic  centimeters  required,  for  any  given  animal, 
to  supply  .0001  Gm.  per  Kgm.  And  since  each  cubic  centimeter  of 
a  I  :  100,000  solution  would  contain  .000.01  Gm.,  a  3.2  Kgm.  cat,  for 
example,  would  require  32  c.c.  Ninety  minutes  being  the  period 
of  injection,  the  proportionate  part  of  the  theoretical  amount  neces- 
sary to  be  run  in  each  minute  or  two  minutes,  was  calculated.  The 
operator  seated  at  the  table,  continued  the  anaesthesia  by  placing 
a  small  pad  of  gauze  over  the  nose  and  supplying  only  sufficient 
ether  to  just  keep  the  animal  quiet.  The  burette  having  been 
filled  and  the  time  noted,  the  injection  was  begun,  running  in  slowly 
every  minute  or  two  minutes  the  amount  proportioned.  The  cat 
was  carefully  watched,  particularly  toward  the  end  when  the  larger 
part  of  the  theoretical  amount  had  been  injected.  Death  was  usually 
preceded  by  very  rapid  respiration  and  decided  convulsive  move- 
m^ents,  after  which  the  respiration  ceased  to  be  regular  and  was 
prolonged  for  a  few  minutes  only  by  gasps.  As  soon  as  these  symp- 
toms of  approaching  death  appeared,  the  injection  was  stopped.  If 
after  waiting  a  few  minutes  the  animal  did  not  die,  the  injection  was 
continued  very  slowly  and  with  great  caution.  When  respiration 
had  ceased  to  be  regular,  the  number  of  cubic  centimeters  of  solution 
used  and  the  time  were  noted,  and  before  the  gasping  had  entirely 
ceased  the  heart  was  exposed.  In  the  majority  of  cases,  rhythmic  con- 
tractions of  the  heart  had  ceased.  Sometimes  the  heart  was  in  feeble 
delirium,  but  usually  the  left  ventricle  was  still  and  the  other  cham- 
bers were  feebly  contracting.  Out  of  twenty-six  experiments  with 
ouabain,  sixteen  with  strophanthus,  and  twenty-seven  with  digitalis, 
only  seven  hearts  were  found  beating  rhythmically,  and  in  these  the 
contractions  were  very  feeble.  Twelve  hearts  showed  the  left  ven- 
tricle in  quite  complete  systole.  It  should  be  remembered  that  reg- 
ular respiration  had  ceased  from  one  to  three  minutes  previous  to 
the  exposure  of  these  hearts.  In  one  instance  under  ouabain,  paral- 
dehyde was  used  as  the  ansesthetic.  (1.8  c.c.  per  Kgm.  Merck's.) 
Immediately  upon  appearance  of  the  gasping,  without  opening 
the  thorax,  artificial  respiration  was  instituted.  The  heart  seemed 
to  improve,  and  continued  to  beat  until  at  the  end  of  ten  minutes 
one  cubic  centimeter  more  of  the  solution  was  slowly  injected  when 
it  stopped.  With  cat  No.  26  artificial  respiration  was  supplied  all 
through  tlie  experiment,  still  the  animal  died  within  the  ninety 
