A^ptJe°m^rPma'}    Manufacture  of  Medicinal  Plasters.  421 
render  action  of  the  medicinal  agents  contained  therein  possible. 
From  a  therapeutic  point  of  view  it  seems  to  be  true  that  a  rubber 
base  plaster  will,  under  some  conditions,  promote,  and  under  other 
conditions  hinder,  absorption. 
Attempts  have  been  made  from  time  to  time  to  produce  ex- 
cipients  which  would  soften  the  base,  also  to  add  mild  detergents 
which  would  soften  the  epidermis  and  thus  assist  in  promoting 
absorption.  Some  years  ago  a  special  line  of  dermal  plasters  was 
offered,  where  a  large  amount  of  drug  was  held  in  perfect  contact 
with  the  diseased  skin,  forming  a  vapor  chamber. 
I  do  not  think  that  the  plaster  makers'  art  has  anywhere  nearly 
reached  its  limit,  we  are  still  looking  for  the  ideal  plaster  mass. 
We  need  a  compound  of  the  peculiar  nature  of  our  present  mass- 
elastic,  adhesive  at  body  temperature,  easy  of  removal,  but  which 
will,  in  addition  to  the  properties  of  the  present  mass,  have  a 
softening  effect  upon  the  skin.  It  would  be  desirable  to  have  a 
mass  which  could  be  compounded  with  a  more  extended  range  of 
medicines.  The  present  rubber  mass  will  not  admit  of  the  use  of 
many  desirable  combinations ;  for  example,  certain  metals,  such  as 
lead,  copper,  iron,  etc.,  cannot  be  compounded  with  the  rubber 
mass.  India  rubber  mass  plasters  are  useless  when  the  medica- 
ment is  a  free  alkaloid.  Oils  and  fats  are  to  a  limited  extent  only 
useful  in  the  rubber  combination. 
The  advantages  of  India  rubber  plaster  mass,  both  for  adhesive 
plasters  and  for  medicated  plasters,  are  well  known.  They  have 
been  summarized  as  follows :  Purified  rubber  is  a  neutral  element, 
and  especially  valuable  as  a  vehicle  for  plasters  on  account  of  its 
great  elasticity  and  flexibility.  India  rubber  preserves  the  incor- 
porated medicaments  from  evaporation  and  from  decomposition. 
India  rubber  is  highly  resistant  to  moisture  and  to  atmospheric 
influences.  It  has  been  stated  by  well-known  therapeutists  that  a 
medicament  properly  combined  with  adhesive  agents  containing 
rubber,  gives  increased  local  action  of  the  incorporated  drug. 
India  rubber  plasters  adhere  closely  to  the  skin;  they  adhere 
at  the  temperature  of  the  body  without  added  heat  or  moisture. 
They  are  perfectly  pliable  at  any  temperature,  and  when  once 
applied  they  do  not  slip  or  move,  and  they  remain  serviceable 
longer  than  any  other  form  of  plaster  mass.  This  latter  state- 
ment is  undoubtedly  true.  Those  who  are  familiar  with  the  rapid 
decomposition  which  takes  place  in  a  resin  and  diachylon  base 
