424  Manufacture  of  Medicinal  Plasters.  {^tSSb^SSL 
below  the  point  named.  India  rubber  is  decomposed  in  the  presence 
of  almost  any  fat,  and  especially  in  the  presence  of  petrolatum. 
India  rubber  is  rapidly  decomposed  under  the  influence  of  heat, 
it  is  also  decomposed  in  the  presence  of  many  metals,  and  it  is 
especially  acted  upon  by  lead.  Such  a  combination,  in  the  course 
of  time,  has  a  tendency  to  harden  and  become  entirely  useless  as 
a  plaster  mass,  and  it  would  be  better  from  a  therapeutic  and 
mechanical  point  of  view  if  the  India  rubber  had  been  omitted 
from  the  formula  altogether.  It  is  my  judgment  that  the  finished 
mass  is  not  at  all  comparable  with  the  diachylon  mass,  or  the  resin 
mass  of  the  former  Pharmacopoeias. 
The  mass  of  the  present  Pharmacopoeia,  when  freshly  made 
and  warm  enough  to  spread,  is  a  soft,  sticky,  unusable  stuff.  It 
is  not  to  be  wondered  at  that  the  profession  have  never  adopted 
plasters  made  by  the  present  Pharmacopceial  methods,  and  that 
they  rely  as  heretofore  upon  India  rubber  plasters,  or  the  resin 
and  lead  plaster  masses. 
In  addition  to  the  plasters  which  I  have  named,  the  U.  S. 
Pharmacopoeia  VIII  has  a  formula  for  mercurial  plaster  made 
up  with  metallic  mercury,  the  oleate  of  mercury,  all  combined 
with  a  lead  plaster  base.  In  this  formula  hydrous  wool  fat  is 
used  for  the  purpose  of  extinguishing  the  mercury.  There  are  also 
given  formulas  for  lead  plaster  and  soap  plaster,  the  latter  being 
a  combination  of  soap  and  a  lead  plaster  base. 
Diachylon  plaster  has  a  fairly  good  sale,  but  inquiry  reveals 
the  fact  that  the  most  of  it  is  purchased  ready  spread  under  the 
types  known  as  Maw's  and  De  La  Cour's.  These  types  correspond 
quite  nearly  to  the  diachylon  plaster  of  the  U.  S.  Pharmacopoeia 
of  1890,  or  the  British  Pharmacopoeia  of  1898,  with  the  addition 
of  a  certain  amount  of  resin. 
The  process  given  for  capsicum  plaster  in  the  last  revision 
directs  that  the  oleoresin  of  capsicum  be  smeared  over  adhesive 
plaster.  This  process  affords  a  convenient  way  of  obtaining  the 
effects  of  capsicum,  and  is  capable  of  considerable  amplification, 
and  points  out  a  method  whereby  medicated  plasters  may  be  pre- 
pared extemporaneously.  Medicaments  usable  as  external  ap- 
plications may  be  brushed  over  the  surface  of  adhesive  plaster 
and  an  infinite  variety  of  medicated  plasters  prepared  at  short 
notice. 
In  this  connection  I  call  attention  to  the  fact  that,  in  addition 
