ju'Se,^?92b.^^^''"'' }      Calcium  Carbonate  in  Medicine.  393 
possibly  the  next  in  general  use  were  crabs  eyes,  or  crabs  stones, 
which  were  known  by  such  terms  as  Lapides  Cancrorum,  Lapilli 
Cancrorum  or  Oculi  Cancrorum,  being  concretions  found  in  the 
stomach  and  consisting  of  about  sixty-four  per  cent,  of  calcium 
carbonate,  with  a  little  animal- matter.  King's  Dispensatory  gives 
the  following  tests  to  distinguish  the  true  from  the  spurious  crab's 
eyes.  They  effervesce  in  hydrochloric  acid  in  which  they  do  not 
completely  dissolve,  thus  being  distinguished  from  spurious  crab's 
eyes,  which  are  wholly  dissolved  by  hydrochloric  acid.  In  the 
presence  of  boiling  water,  crab's  eyes  assume  a  pinkish  red  hue. 
Another  closely  related  product  was  crab's  claws,  Chelae  Can- 
crorum, which  were  prepared  in  a  finely  powdered  state  and  con- 
sisted of  about  sixty  per  cent,  of  calcium  carbonate. 
Corallen  or  Coral,  was  still  another  of  the  forms  of  calcium  car- 
bonate used,  and  this  too  is  still  used  in  the  Homoeopathic  Pharma- 
copoeia, under  the  name  Corallium  Rubrum,  or  red  coral,  the  skeleton 
of  the  coral  zoophyte.  The  chemical  constituents  are  calcium  car- 
bonate with  a  trace  of  magnesium  carbonate  and  a  little  more  than 
four  per  cent,  of  ferric  oxide  as  coloring  matter.  There  is  a  small 
amount  of  animal  matter  present.    This  is  also  called  carail  rouge. 
Os  sepia,  or  cuttlefish  bone,  the  mantle  of  Sepia  Officinalis  L., 
is  still  another  of  the  many  forms  of  calcium  carbonate  relied  upon. 
This  consists  of  from  eighty  to  eighty-five  per  cent,  of  calcium  car- 
bonate. Its  use  lies  mainly  in  furnishing  calcium  carbonate  to  cage 
birds. 
An  interesting  note  on  lime  water  dating  back  to  the  nineteenth 
century,  states  that  lime  water  was  originally  prepared  from  "cal- 
caria  usta,"  as  lime  was  called,  and  the  preparation  was  known  as 
"Aqua  Calcaria  Usta." 
Other  waters  of  this  nature  were  mentioned  linder  such  names 
as  aqua  calcarea  bicarbonica,  aerated  or  carbonated  lime  water,  and 
aqua  magnesia  carbonica.  Aqua  or  liquor  magnesia  carbonica  was 
made  either  by  freshly  precipitating  magnesium  carbonate  from 
magnesium  sulphate  and  sodium  carbonate  and  saturating  with  car- 
bon dioxide,  or  using  magnesia  alba  directly  and  then  saturating. 
