392  Calcium  Carbonate  in  Medicine.      { jJSe,"^i92o.^*'^'''"* 
The  method  for  preparing  precipitated  chalk  was  first  made 
official  in  the  fourth  edition,  1850,  of  the  U.  S.  Pharmacopoeia, 
while  the  prepared  chalk  was  official  in  the  first  and  second  editions, 
as  Calcis  Carbonas  Praeparatus,  and  the  title  changed  to  the  present 
form  of  Creta  Praeparata  in  the  third  edition,  1840.  Likewise 
Mistura  Calcis  Carbonatis  was  official  in  the  first  two  editions  of 
the  Pharmacopoeia,  and  was  changed  to  Mistura  Creta  in  the  third 
edition.  The  U.  S.  Dispensatory,  first  edition,  1833,  also  added, 
that  besides  being  official  in  its  soft  state,  as  chalk,  carbonate  of 
lime  is  also  ordered  as  it  exists  in  marble  (marmor),  oyster  shells, 
crabs  eyes  and  crabs  stones.  The  preparation  called  Testa  Pre- 
parata,  was  recognized  in  the  U.  S.  Pharmacopoeia  from  the  first 
to  the  sixth  editions  inclusive.  Testa  is  the  term  applied  to  the 
shell  of  the  oyster,  Ostrea  Edulis,  L.,  consisting  of  about  eighty- 
seven  to  ninety-eight  per  cent,  of  calcium  carbonate  and  found 
mostly  in  the  internal  pearly  layer  of  the  shell.  Conchae  was 
another  term  used  to  designate  oyster  shells,  prepared  by  boiling 
with  water  and  freed  from  all  foreign  matter,  and  Conchae  Pre- 
paratae,  the  purified  oyster  shell,  purified  by  elutriation  and  tro- 
chiscation. 
At  the  present  time  there  is  a  preparation  of  this  type  official  in 
the  Homoeopathic  Pharmacopoeia,  by  the  name  of  Calcarea  Car- 
bonica,  or  Calcium  Carbonate  of  Hahnemann,  and  is  sometimes 
known  as  Calcarea  Ostrearum,  or  Testa  Ostryae.  This  is  impure 
carbonate  of  lime  as  it  exists  in  the  oyster  shell,  and  is  directed  to 
be  prepared  as  follows:  Take  well  selected,  tolerably  thick  oyster 
shells,  clean  and  break  in  a  wedgewood  or  porcelain  mortar.  Select 
the  pure  white  portions  which  exist  between  the  interior  and  ex- 
terior surfaces,  wash  carefully  in  distilled  water,  dry  over  a  water 
bath  and  reduce  to  a  fine  powder. 
According  to  theories  accepted  at  that  time,  testa  was  supposed 
to  be  more  acceptable  to  the  stomach  than  ordinary  chalk.  Lewis' 
Materia  Medica,  1784,  states  that  lime  water  dissolves  the  human 
calculus,  particularly  lime  water  prepared  from  calcined  oyster 
shells,  which  proves  a  more  active  menstruum  for  this  concrete 
(and  possibly  other  substances)  than  that  prepared  from  stone  limes, 
the  dissolving  power  of  oyster  shell  lime  water  seeming  to  be  more 
than  double  that  of  stone  lime  water. 
There  were  a  great  many  other  drugs,  besides  oyster  shells, 
which  were  used  at  various  times  as  sources  of  calcium  carbonate,  and 
