410  Standard  for  Desiccated  Thyroid  G  lands  \^^'^^J^^^;J^^^^- 
From  the  above  results  it  is  found  that  the  average  of  the  12 
P.  D.  &  Co.  samples  received  in  1907  is  0.171  per  cent.  I,  while 
that  for  the  Armour  samples  is  0.138  per  cent.  On  the  other  hand 
the  average  per  cents,  for  the  recent  samples  are  respectively  0.195 
and  0.202,  thus  showing  that  in  both  cases  products  with  higher 
iodine  contents  are  being  prepared.  On  the  whole  these  results 
show  a  very  commendable  degree  of  regularity  in  the  percentage  of 
iodine  in  thyroid  at  present  on  the  market.  With  very  few  ex- 
ceptions none  of  these  samples  might  be  expected  to  produce  a 
noticeable  variation  in  physiological  effect.  There  can  be  no  doubt, 
however,  that  the  interests  of  both  the  producer  and  consumer 
would  be  safeguarded  by  the  establishment  of  a  reasonable  Pharma- 
copoeial  standard  of  iodine  content.  Judging  from  the  results  upon 
the  samples  supplied  by  the  manufacturers  themselves,  such  a  limit 
could  be  fixed  at  approximately  0.2  per  cent.  1.  without  causing  an 
undue  hardship.  This  per  cent,  has  already  been  adopted  by  an 
English  firm.  Of  course  sufficient  latitude,  of  say  0.03  per  cent, 
above  or  below  this  figure,  should  be  permitted,  thus  making  the 
extreme  limits  0.17  to  0.23  per  cent,  iodine. 
The  remaining  Pharmacopoeial  description  which  is  necessary 
is  that  limiting  the  source  of  the  raw  material  to  certain  animals 
and  prescribing  a  reasonable  limit  of  moisture  and  ash,  which  from 
our  experiments  might  be  placed  at  not  exceeding  6  per  cent,  for 
the  former  and  5  per  cent,  for  the  latter,  and  finally  the  prohibition 
of  all  iodine  in  inorganic  or  any  other  form  of  combination  than 
that  peculiar  to  the  thyroid. 
In  regard  to  the  ash  content  it  should  be  mentioned  that  in 
general  those  samples  with  the  higher  percentage  of  iodine  contain 
the  lower  percentage  of  ash,  and  vice  versa.  Thus  for  instance, 
of  12  samples  containing  more  than  0.2  per  cent,  iodine  the  variation 
in  the  ash  content  was  from  only  3  to  4  per  cent.,  while  6  samples 
containing  approximately  0.15  per  cent,  iodine  contained  more  than 
4  per  cent,  ash,  and  one  sample  with  only  0.095  per  cent,  iodine 
contained  more  than  5  per  cent,  of  ash. 
It  has  recently  been  suggested  by  certain  investigators  that  the 
iodine  of  thyroid  may  not  all  be  present  in  an  equally  physiologically 
active  form,  and  consequently  that  it  was  possible  by  certain 
manipulative  processes  to  remove  the  less  active  forms  and  retain 
the  more  active  portion  in  a  product  which  is  therefore  supposed  to 
contain  iodine  in  a  super  active  condition  as  compared  with  that 
