58 
Preparation  of  Thyroid  Extract. 
f  Am.  Jour.  Pbarm. 
(    February,  1911, 
DOES  THYROID  PROTEID  FREE  FROM   IODINE  HAVE  ANY  FUNCTIONAL 
ACTIVITY  ? 
This  is  an  old  question  and  it  has  been  the  opinion  of  many 
experimenters  from  Banmann,  Miwa,  Stoeltzner,  and  Neumeister, 
and  it  has  recently  been  reiterated  by  John,  that  because  many  in- 
stances of  iodine-free  thyroids  were  found  in  animals  enjoying 
apparent  health,  that  therefore  no  essential  relation  exists  between 
iodine  content  and  physiologic  action.  Hunt  ^  has  modified  this 
opinion  somewhat  by  concluding-  that  iodine-free  thyroid  has  a  mild 
deg-ree  of  activity,  but  that  it  is  not  to  be  compared  with  normal 
iodized  thyroid  in  its  protective  power  to  acetonitril  poisoning. 
Such  a  conclusion  as  well  as  that  of  the  older  investigators  is, 
however,  open  to  the  criticism  that  the  methods  for  determining 
the  presence  of  iodine  may  have  been  faulty.  A  large  number  of 
thyroid  glands  have  been  analyzed  for  iodine  in  this  laboratory  dur- 
ing the  last  three  years  and  we  have  not  found  any  which  were  abso- 
lutely iodine  free.  There  is  no  question  that  such  a  finding  is  due 
to  an  improvement  in  the  Baumann  method  of  iodine  determination. 
According  to  the  Baumann  method  the  thyroid  tissue  is  fused 
in  a  nickel  crucible  with  sodium  hydroxide  and  sodium  nitrate. 
Only  sufficient  sodium  nitrate  is  used  to  give  a  clear  fusion  mass. 
The  melt  is  dissolved  in  water,  acidified  with  sulphuric  acid,  nitrous 
acid  added  to  set  free  the  iodine,  which  is  shaken  out  with  chloro- 
form or  carbon  bisulphide  and  estimated  colorimetrically.  Dr.  L. 
W.  Riggs,^  working  in  this  laboratory,  has  shown  that  during  the 
fusion  process  a  variable  amount  of  the  iodine  is  oxidized  to  iodate, 
which  is  not  subsequently  reduced  by  the  nitrous  acid,  and  which, 
therefore,  is  lost  in  the  extraction  with  carbon  tetrachloride  and  gives 
too  low  a  reading. 
5  Nal  +  NalO,  +  3H,  SO,  — >    3L  +  3Na,  So,  -f  3H2O 
According  to  the  above  reaction  five  molecules  of  iodide  set  free 
the  iodine  from  one  molecule  of  iodate,  and  it  follows  that  where 
the  proportion  of  iodate  is  greater  than  this  some  of  it  must  remain 
undetermined.  When  small  quantities  of  iodine  are  present  in  the 
fusion  mass  a  relatively  larger  proportion  of  the  iodine  is  oxidized 
to  iodate  and  the  proportion  of  one  molecule  of  iodate  to  five  of 
iodide  is  exceeded,  with  a  consequence  that  iodine  is  lost.  When  only 
very  small  quantities  of  iodine  are  present  it  may  be  entirely  oxi- 
dized, and  a  report  given  of  no  iodine  found  in  the  gland.  The 
