Am.  Jour.  Pharm.  1 
Nov.  1, 1872.  j 
Gantharides. 
501 
excellent  theory,  but  in  practice  abounds  with  so  many  obstacles  and 
yields  such  an  unexpectedly  inferior  result,  that  the  writer  believes, 
should  other  operators  be  equally  unsuccessful,  it  will  never  attain 
to  popularity. 
A  good  quality  of  cantharides  in  very  fine  powder  was  digested 
with  an  aqueous  solution  of  potassium  hydrate,  then  treated  with  a 
slight  excess  of  chlorhydric  acid,  dried  and  converted  into  cerate  ac- 
cording to  the  pharmacopoeia.  The  resulting  product  was  destitute 
of  vesicating  power. 
However,  the  failure  to  produce  blisters  with  this  preparation,  the 
writer  is  not  inclined  to  charge  entirely  to  Prof.  DragendorfFs  part 
of  the  process.  The  writer  has  found  that  a  water-bath  heat,  as  offi- 
cinally  directed,  is  often  inadequate  to  dissolve  the  necessary  amount 
of  cantharidin  for  producing  an  active  plaster.  But  by  following  the 
suggestion  of  Mr.  Donovan,  to  use  an  increased  and  prolonged  heat, 
a  desirable  plaster  is  most  usually  obtained. 
The  chief  incumbrances  to  Prof.  DragendorfFs  process  are  : 
Firstly.  That  the  aqueous  alkaline  solution  produces  with  the  pow- 
dered cantharides  a  doughy  mass  not  easily  manipulated,  and  to  bring 
this  into  a  sufficiently  fluid  condition  which  the  nature  of  the  opera- 
tion demands,  an  excessive  quantity  of  alkaline  solution,  equal  to 
about  three  times  the  weight  of  the  cantharides,  is  necessarily  ab- 
sorbed. The  large  surplus  of  alkali  again  requires  a  proportionate 
amount  of  chlorhydric  acid  for  neutralization. 
Secondly.  This  mass,  if  a  considerable  quantity  is  under  treatment, 
is  not  so  easily  dried,  as  exposure  in  the  open  air  without  artificial 
heat  is  entirely  inadmissible  by  reason  of  the  rapid  formation  of  mould. 
The  subsequent  powdering  of  the  dried  mass  is  another  unpleasant 
operation  which  pharmaceutists  always  endeavor  to  evade,  especially 
as  in  this  case  the  requirement  is  a  repetition.  The  unsuccessful 
issue  of  the  operation  excites  a  doubt  whether  after  all  the  canthari- 
din thus  liberated  is  as  soluble  in  the  fatty  excipient  as  it  would  be 
in  its  natural  state  of  combination  when  subjected  to  an  elevated  tem- 
perature. When  the  prepared  cantharides  is  not  thoroughly  dry,  or 
if  the  fatty  matter  contains  moisture,  the  cerate  invariably  and  rap- 
idly develops  an  exuberant  growth  of  mould,  but  it  was  found  that 
the  presence  of  moisture  in  either  good  or  defective  cerate  neither 
aided  or  detracted  from  the  activity  ;  because  a  good  cerate  made  by 
the  ordinary  method  may  become  mouldy  from  the  presence  of  water 
