Amju0nue?if9hiarm-}         Salts  of  Cantharidinic  Acid.  297 
tharides  varying  from  -3  to  -6  per  cent. ;  Liebreich,  therefore,  deter- 
mined to  employ  the  active  principle  itself. 
The  exact  constitution  of  cantharidin  (C10H12O4)  has  not  been 
determined,  but  of  the  oxygen  atoms  contained  there  is  reason  for 
believing  that  three  of  the  atoms  are  contained  in  the  group  CO 
and  COOH. 
Many  derivatives  have  been  obtained  from  it,  as  for  example : 
Cantharidinic  acid,  CJ0H14O5 
Cantharidoxim,  C10H13NO4 
Cantharidoximic  acid,  .  .  '.  C10H15NO5 
Cantharic  acid,  C10H12O4 
Cantharoximic  acid,  C10H13NO4 
To  avoid  complications  arising  from  the  irritant  action  of  cantha- 
ridin on  the  stomach  and  intestines,  it  seemed  desirable  to  inject 
it  subcutaneously.  But  cantharidin  is  not  soluble  in  water,  though 
dissolved  by  ether  and  oils.  Cornil  has  used,  in  experiments  on 
animals,  a  solution  in  acetic  ether,  and  Aufrecht  a  solution  in  oil ; 
but  the  former  solvent  is  irritating,  whilst  the  oily  solution  is  not 
adapted  to  subcutaneous  injection.  Cantharidin  can  also  be  dis- 
solved in  caustic  potash  and  soda,  being  at  the  same  time  in  part 
converted  into  cantharidinate  of  the  alkali. 
Cornil  had  stated  that  the  potash  solution  causes  suppuration,  but 
Liebreich  found  that  this  was  due  to  the  excess  of  alkali  used,  and 
that  by  employing  the  smallest  amount  of  alkali  which  would  dis- 
solve the  cantharidin,  a  satisfactory  material  was  obtained  for  sub- 
cutaneous use.  He  commenced  the  use  of  cantharidin  dissolved  in 
potash  by  giving  ^  of  a  milligramme  (3-5^  grain),  which  caused 
neither  pain  nor  redness  at  the  point  of  injection,  and  gradually 
increased  the  dose,  but  found  it  could  not  be  raised  higher  than 
of  a  milligramme  (TJ-g-  grain)  without  producing  urinary  troubles. 
On  injecting  a  series  of  tubercular  laryngitis  with  a  solution  of 
cantharidin  in  caustic  potash,  such  distinct  improvement  was 
observed  that  Liebreich  thinks  there  can  be  no  doubt  of  the  cura- 
tive influence  of  the  drug,  though  further  clinical  observations  are 
required  to  determine  the  limits  of  its  value. 
On  an  average  a  solution  of  1  cc,  containing  T2^  of  a  milligramme 
(o-J-g-  gr.)  of  cantharidin  was  injected  into  the  back.  No  febrile 
reaction  or  redness  of  the  affected  part  was  observed. 
He  advises  that  should  diarrhoea  or  a  burning  feeling  of  the 
