Am.  Jour.  Pharm. 
June,  1919. 
Pharmacy  of  Tethelin. 
353 
Aqueous  solutions  of  tethelin  are  faintly  acid  in  reaction. 
Tethelin  is  soluble  in  ethyl  alcohol  and  to  a  less  extent  in  ethyl 
ether,  the  solutions  in  ether  being  marked  by  opalescence  at  high 
dilutions.  It  is  also  soluble  in  chloroform  and  in  carbon  tetrachlo- 
ride. It  is  insoluble  in  a  mixture  of  one  part  by  volume  of  absolute 
ethyl  alcohol  and  one  and  one  half  parts  of  dry  ether.12 
When  ignited  until  free  from  carbon,  tethelin  yields  a  few  per 
cent,  of  ash. 
The  exact  chemical  nature  and  structural  formula  of  tethelin 
have  not  as  yet  been  thoroughly  established.  It  partakes  of  the 
nature  of  a  lipoid.  It  is  capable  of  being  saponified  by  alkalies  and 
possesses  iodine-absorption  properties.  It  contains  phosphorus  and 
nitrogen.  Part  of  the  nitrogen  is  in  the  amino  form.  The  propor- 
tion of  amino  nitrogen  is  increased  after  hydrolysis  by  barium  hy- 
droxide. Among  the  products  yielded  by  hydrolysis  with  barium 
hydroxide  followed  by  hydrolysis  with  dilute  sulphuric  acid,  is  ino- 
site.  The  presence  of  both  phosphorus  and  inosite'm  tethelin  is  of 
great  interest  in  view  of  the  presence  of  "phytin"  (inosite-hexa- 
tphosphoric  acid)  in  the  rapidly  growing  parts  of  plants  and  in  milk, 
and  its  probable  importance  in  connection  with  the  growth  of  tis- 
sues. Tethelin  probably  contains  an  iminozolyl  group  and  to  this 
extent  may  be  regarded  as  being  related  to  the  physiologically  active 
substances  of  the  posterior  lobe  of  the  pituitary  body.  It  does  not, 
however,  possess  the  characteristic  physiological  activity  of  these 
substances.13 
Precautions  to  be  Observed  in  Dispensing  Tethelin. 
Tethelin  in  dry  form  should  at  all  times  be  preserved  in  a  sealed 
glass  tube  in  which  a  vacuum  has  been  created.  It  is  extremely 
hygroscopic,  the  moisture  of  the  air  being  readily  absorbed  by  it 
and  thereby  lowering  its  activity  in  proportion  to  the  quantity  of 
moisture  absorbed. 
In  addition  it  is  also  extremely  prone  to  oxidation  upon  exposure 
to  air.  Robertson  advocates  the  use  of  vacuum  tubes  which  contain 
100  Mgm.,  since  this  is  the  quantity  which  is  generally  accepted  as 
being  satisfactory  for  use  at  one  time. 
It  is  most  desirable  that  the  whole  of  the  contents  of  a  tube  of 
tethelin  be  employed  when  the  tube  is  opened  and  that,  under  no 
12  Robertson,  T.  B.,  Jour.  Biolog.  Chem.,  1916,  XXIV,  p.  411. 
13  Robertson,  T.  B.,  Jour.  Biolog.  Chem.,  1916,  XXIV,  pp.  409-421. 
