n8  Standardization  of  Digitalis  Bodies.    { 5grm' 
kg.  by  ten  and  divide  by  ninety,  the  theoretically  appropriate  dura- 
tion of  the  injection  in  minutes,  and  the  resulting  figure  will  be 
the  number  of  c.c.  to  be  injected  per  minute.  But  as  we  are  dealing 
with  an  estimated  activity  of  100  mg.  per  kg.  it  is  not  necessary  to  go 
through  this  elaborate  calculation,  for  the  multiplication  by  100 
at  first  is  about  neutralized  by  the  subsequent  division  of  the  result 
by  ninety,  so  that  he  has  merely  to  inject  a  number  of  c.c.  per  minute 
equal  to  one-tenth  of  the  weight  of  the  cat  in  kg. 
After  all  of  this  discourse  on  the  exact  or  approximate  estimation 
of  the  time  of  the  injection  and  its  rate,  I  would  say  that  in  the 
years  during  which  the  method  has  been  in  use  in  this  laboratory 
injections  have  been  made  over  periods  varying  from  ten  minutes 
to  three  or  four  hours  and,  save  for  the  likelihood  of  "running 
over"  in  the  case  of  the  shorter  period,  the  duration  has  shown 
little  or  no  appreciable  effect  upon  the  ultimate  dose  required.  It  is 
not  to  be  understood,  however,  that  such  wide  differences  are 
advocated,  they  are  merely  mentioned  to  show  that  great  nicety  in 
the  estimation  of  the  rate  of  injection  is  quite  unnecessary.  All  that 
is  required  is  that  the  injection  shall  be  slow  enough  to  reduce  the 
likelihood  of  greatly  exceeding  the  minimum  fatal  dose  and  rapid 
enough  to  avoid  such  theoretical  factors  as  the  possible  excretion  of 
some  of  the  drug  or  of  seriously  injuring  the  heart  through  pro- 
longed anesthesia.  Injections  lasting  6  hours  have  given  results 
somewhat  too  high. 
The  cat  method  has  been  said  to  be  so  time  consuming  that  it 
is  impossible  to  make  a  standardization  of  more  than  one  specimen 
in  a  single  day.   The  following  is  an  answer  to  this  contention: 
Eight  cats  were  obtained  from  Ithaca,  N.  Y.,  for  the  sake  of 
testing  the  reaction  of  animals  from  outside  of  the  city. 
At  9.00  A.M.  the  laboratory  helper  began  to  weigh  the  animals 
and  prepare  burettes,  boards,  instruments,  etc.,  for  their  testing. 
At  the  same  time  an  accurate  solution  of  ouabain  was  prepared. 
When  these  preliminaries,  including  the  filling  of  the  8  burettes, 
were  completed  an  animal  was  etherized  and  tied  to  a  board.  While 
the  operator  was  exposing  the  femoral  vein  and  inserting  the  can- 
nula connected  with  the  burette  a  second  cat  was  being  etherized 
and  by  the  time  it  had  been  tied  on  a  board  the  first  injection  had 
been  started  and  a  record  made  of  the  time  on  the  slip  on  which 
the  boy  had  written  the  weight  and  description  of  the  animal.  In 
this  manner  all  of  the  8  animals  were  prepared  and  the  injection 
begun  in  each,  with  an  average  of  7  minutes  needed  for  the  com- 
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