AmM°ay!'  fgia7rm'  )  U'  S-  P-  Standard  for  Pituitary  Extract.  IQ9 
and  are  repeated  every  twenty  to  thirty  minutes,  depending  upon 
the  time  required  for  relaxation  by  the  given  organ,  approximately 
the  same  period  of  application  being  maintained  for  each  uterus 
throughout  the  experiment.  A  dilution  of  the  pituitary  solution  is 
sought  which  will  produce  contractions  equal  to  those  recorded 
under  the  standard. 
Manner  of  Making  Dilutions. 
It  should  be  understood  that  when  "  pituitary  extract "  is  men- 
tioned in  this  paper  the  commercial  solution  is  referred  to.  The 
dilutions  are  made  as  follows:  .1  Cc.  of  the  pituitary  extract  or 
solution  is  drawn  from  the  ampoule  by  means  of  a  narrow  pipette 
and  diluted  with  distilled  water  to  100  Cc.  in  a  volumetric  flask. 
This  makes  a  I  :  1,000  dilution.  I  use  distilled  water  in  this  place, 
believing  that  the  dilution  so  made  will  not  lose  strength  materially 
during  the  experiment  of  five  or  six  hours.  The  deterioration  of 
pituitary  extract  in  Locke's  solution  has  been  mentioned  by  Fenger 
(3).  When  it  is  desired  to  apply  say  a  1:200,000  dilution  to  the 
uterus,  .5  Cc.  of  this  1  :  1,000  dilution  is  drawn  off  and  added  to  the 
100  Cc.  chamber.  The  Locke's  solution  in  the  chamber  is  kept  at 
such  a  height  that  when  the  pituitary  dilution  is  added,  the  100  Cc. 
mark  will  have  been  approximately  reached.  If  a  trifle  more 
Locke's  solution  is  needed,  it  is  allowed  to  flow  gently  into  the  cham- 
ber from  the  reservoir.  The  dilutions  of  pituitary  extract  are  meas- 
ured out  with  a  narrow  pipette  into  a  small,  conical,  glass  cup  and 
diluted  with  enough  Locke's  solution  to  make  about  1  Cc.  From 
this  glass  the  dilution  is  taken  up  with  a  "  Record  "  syringe  having 
a  long  needle,  and  introduced  into  the  chamber,  the  glass  and 
syringe  being  afterward  rinsed  with  another  1  Cc.  of  Locke's  so- 
lution. 
The  beta-imidazolylethylamine  hydrochloride  was  supplied  by 
the  Hoffman-La  Roche  .Co.  .05  gram  of  this  substance  taken 
from  the  1  gram  vials  as  supplied,  without  desiccating  (being  appar- 
ently dry),  is  placed  in  a  sterile  500  Cc.  volumetric  .flask  and  dis- 
solved in  freshly  boiled  and  cooled  distilled  water  containing  a  small 
amount  of  acetof orm  and  made  up  to  mark.  This  1  :  10,000  dilution 
is  sealed  in  ampoules  and  kept  in  a  refrigerator  in  the  dark.  It 
seems  to  keep,  thus,  for  many  months  without  noticeable  deteriora- 
tion.   For  use  10  Cc.  are  diluted  to  100  Cc.  in  a  volumetric  flask. 
