Am.  Jour.  Pharm. 
June,  1919. 
Pharmacy  of  Tethelin. 
355 
Tethelin  normally  forms  a  turbid  solution  with  water,  therefore 
no  attempt  should  be  made  to  filter  the  solution  perfectly  clear. 
Extraneous  particles  of  foreign  matter  such  as  fibers,  particles  of 
dust,  glass,  etc.,  which  may  accidentally  find  their  way  into  a  solu- 
tion, while  it  is  in  process  of  preparation,  may,  of  course,  be  re- 
moved by  rapid  filtration  of  the  solution  under  perfectly  sterile  con- 
ditions. It  is,  however,  quite  unnecessary  to  labor  to  attain  a  per- 
fectly clear  filtrate,  before  use.  The  same  care  must  be  exercised 
in  regard  to  sterility,  in  preparing  a  solution  for  local  use  as  for 
hypodermic  use.  Aqueous  solutions  of  tethelin  are  faintly  acid  in 
reaction.  The  acidity  of  tethelin  is  one  of  its  chemical  characteris- 
tics and  is  so  slight  as  to  have  no  corrosive  effect  whatever  upon 
metallic  hypodermic  syringes. 
Schmidt14  found  that  B.  coli  and  B.  proteus  could  grow  in  a 
medium  containing  1  per  cent,  of  tethelin  and  a  trace  of  salt. 
A  quantity  of  tethelin  in  a  semi-dry  state  which  was  contributing 
to  the  growth  of  B.  Hay  has  come  under  my  observation. 
The  fact  that  a  solution  of  tethelin  is  a  culture  medium  for  cer- 
tain bacteria  indicates  the  necessity  of  employing  only  freshly  ster- 
ilized and  cooled  distilled  water  in  the  manufacture  of  its  solutions. 
The  same  is  true  of  any  other  liquid  or  semi-liquid  vehicles  as 
might  be  employed,  such  as  ointment  bases  for  the  manufacture  of 
ointments  of  tethelin.  These  bases  should  be  rendered  sterile  at 
ioo°  C,  and  should  be  cooled  before  the  tethelin  is  incorporated. 
Tethelin  solutions  and  any  extemporaneous  preparations  of 
tethelin  must  be  freshly  prepared  and  not  kept  as  stock  solutions  or 
preparations.  The  difficulties  of  keeping  stock  solutions  and  stock 
preparations  of  tethelin  sterile  under  the  conditions  usually  obtain- 
able outside  of  a  bacteriological  laboratory  are  quite  insurmountable 
because  of  the  extreme  readiness  with  which  certain  microorganisms 
make  use  of  tethelin  for  their  growth. 
Precautions  to  be  Observed  in  Using  Tethelin. 
Tethelin  is  lipoid  in  nature  and  as  a  consequence  is  subject  to 
hydrolysis  in  the  presence  of  alkaline  substances.  For  this  reason, 
it  is  not  advisable  to  employ  it  in  admixture  with  such  more  or  less 
alkaline  wound  dressings  as  neutral  sodium  oleate,  soaps,  sodium 
phenolate,  calamine,  zinc  oxide,  ichthyol,  sodium  hypochlorite,  sodium 
14  Schmidt,  Carl  L.  S.,  Ph.D.,  Jour.  Lab.  and  Clin.  Medicine,  1917,  II, 
p.  717. 
