554  Active  Principle  of  Suprarenal  Gland.  { ^n^.^Xr^'f^T^ 
resulting  solution  diluted  to  the  required  strength  than  when  a 
proportionately  smaller  amount  of  sample  was  used  and  the  solu- 
tion not  diluted. 
With  samples  containing  from  0.2  to  0.8  per  cent,  of  the  active 
principle,  o.oi  gm.  is  placed  in  a  test  tube  with  5  c.c.  of  dilute  HCl 
(2.5  c.c.  0.1  n  HCl  per  100  c.c.)  and  5  c.c.  of  0.2  per  cent.  KIO.j 
solution,  the  mixture  heated  just  to  the  boiling  point  and  allowed 
to  stand  1 5  minutes ;  it  is  then  filtered  and  the  color  compared  with 
the  series  of  standards  corresponding  to  o.oi  to  o.io  mg.  per  10  c.c. 
The  position  of  the  unknown  can  in  practically  all  cases  be  fixed  in 
this  series  with  reasonable  certainty. 
Determinations  were  made  as  above  described  upon  nine  samples 
of  commercial  desiccated  suprarenals  obtained  from  two  firms  and 
one  sample  of  i  :  1,000  solution  of  the  active  principle  which  had 
been  in  the  laboratory  some  time.    The  results  were  as  follows : 
Table  I. 
Per  cent. 
Sample  No.  active  principle. 
362   0.6 
363   0.6 
364   0-6 
365   0.8 
366   0.2 
367   0.8 
368   0.4 
369   0.4 
370   less  than  0.03 
I  :  1,000   solution  0.03. 
THE   PHYSIOLOGICAL  EXPERIMENTS. 
In  the  quantitative  physiological  assay  of  epinephrine  a  number 
of  different  methods  have  been  proposed,  all  being  based  on  some 
physiological  action  of  the  base.  Of  these  the  one  most  commonly 
employed  is  that  of  determining  the  relative  rise  in  blood  pressure 
as  compared  with  a  given  amount  of  the  pure  base ;  and  a  careful 
analysis  of  the  other  methods,  the  frog's  eye  test,  the  use  of  arterial 
strips  and  the  minimum  lethal  dose,'^  indicates  that  with  proper 
precautions  this  is  also  the  most  satisfactory  and  accurate.  Of  the 
several  animals  upon  which  blood  pressure  experiments  might  be 
carried  out  dogs  appear  to  give  the  best  results.    For  the  purpose 
'  Schultz :  Bull.  55,  Hyg.  Lab.,  U.  S.  P.  H.,  and  M.  H.  S.,  1909. 
