^DecSerffwT*}  AcHve  Principle  of  Suprarenal  Gland.  555 
of  these  tests  full  grown  dogs  of  small  size,  5  to  10  kilograms  body 
weight,  were  chosen.  They  were  anaesthetized  by  the  injection  of 
0.015  gm.  morphine  sulphate  per  kilo,  and  sufficient  ether  given  to 
insure  complete  anaesthesia  during  the  operative  procedure.  The 
ether  was  then  withdrawn  although,  if  the  animal  showed  signs  of 
returning  consciousness,  especially  as  noted  by  irregularities  in  the 
blood  pressure  curve,  it  was  again  administered  in  small  quantities 
during  the  course  of  the  experiment.  A  cannula  was  introduced  into 
the  carotid  and  connected  with  a  mercury  manometer  to  secure  a 
blood  pressure  tracing.  Cannulae  were  also  introduced  at  the  same 
level  into  both  the  right  and  left  femoral  veins  for  the  injection  of 
the  drug  to  be  tested.  Both  vagi  were  cut  and  artificial  respiration 
maintained  throughout  the  experiment. 
To  prepare  the  desiccated  suprarenal  extract  for  injection  50 
milligrams  were  added  to  40  c.c.  Ringer  solution  and  acidulated 
by  the  addition  of  3  drops  of  10  per  cent.  HCL  This  was  then 
slowly  brought  to  a  boiling  temperature  and  allowed  to  cool  for 
ten  minutes,  whereupon  the  solution  was  passed  through  a  filter 
and  the  residue  washed  with  a  sufficient  amount  of  warm  Ringer 
solution  to  bring  the  total  up  to  50  c.c,  thus  making  i  c.c.  of  the 
solution  represent  i  milligram  of  the  desiccated  gland.  This  pro- 
cedure, however,  was  altered  in  the  case  of  two  samples,  Nos.  366 
and  370,  owing  to  their  relative  inactivity.  These  samples  were 
each  made  up  so  that  i  c.c.  of  the  resulting  solution  equalled  5 
milligrams  of  the  gland,  thus  securing  a  suitable  rise  in  pressure 
without  using  too  large  doses  for  intravenous  injection. 
The  rise  in  pressure  from  equal  doses  of  the  same  preparation 
varies  in  different  animals  and  in  the  same  animal  from  time  to 
time  during  the  experiment.  This  is  probably  due  in  large  measure 
to  a  varying  depth  of  anaesthesia  and  to  varying  sensitiveness  of  the 
vasomotor  centre  and  the  musculature  of  the  arterioles.  At  any  rate 
it  becomes  necessary  in  quantitative  work  to  inject,  alternately  with 
the  sample  which  is  being  assayed,  a  definite  amount  of  the  purified 
base,  continuing  in  this  until  rises  of  equal  height  are  obtained.  As 
duplicate  determinations  there  should  then  be  injected  ratios  of  the 
amount  necessary  to  produce  the  same  result  and  these  larger  or 
smaller  amounts  of  the  known  and  the  unknown  solution  should 
likewise  produce  equal  rises  in  pressure.  Many  of  the  necessary 
details  of  this  method  have  been  discussed  by  Dr.  Schultz  in 
Hygienic  Laboratory  Bulletins  Nos.  55  and  61. 
