COMPOSITION  OF  THE  AQUA  LAURO-CERASI. 
447 
tains  is  uncertain.  It  is  stated  by  some  writers  to  contain  2.75 
per  cent.  ;  while  according  to  others  who  have  investigated  the 
subject,  it  may  exist  in  as  large  a  proportion  as  7.66  per  cent. 
Christison  confirms  this  discrepancy,  he  having  obtained  from 
developed  young  leaves  twice  as  much  acid  as  from  old  ones. 
Then,  again,  while  it  is  well  known  that  the  leaves  are  con- 
stantly employed  with  impunity  as  a  flavoring  for  articles  of 
food,  many  cases  have  occurred  in  which  serious  results  have 
supervened  from  their  use  in  this  manner.  In  a  case  cited  by 
Dr.  Paris,  several  children  were  nearly  poisoned  by  eating  a 
custard  so  flavored.  Zeller  states  that  the  leaves  gathered  in 
wet  cold  weather  yield  more  hydrocyanic  acid  than  when  they 
are  collected  in  a  hot,  dry  season. 
From  this  collection  of  facts  it  will  be  seen  that  it  is  impossi- 
ble for  any  two  samples  of  laurel  water  to  contain  the  same  pro- 
portion of  active  constituents,  but  this  is  by  no  means  the  only 
source  of  error.  Others  which  are  no  less  conducive  to  uncer- 
tain composition  creep  in  during  the  process  of  manufacture. 
As  the  whole  of  the  oil  comes  over  in  the  distillation  with  the 
first  few  ounces  of  water,  if  the  whole  product  be  not  strongly 
agitated  before  filtration,  a  uniform  preparation  will  not,  even 
if  other  conditions  be  favorable,  be  obtained.  Moreover, 
constant  variations  from  the  process  given  by  the  Pharma- 
copoeias are  frequently  adopted  to  suit  the  conveniences  of  manu- 
facture on  the  large  scale.  The  most  usual  of  these  modifica- 
tions consists  in  passing  steam  through  a  vessel  containing  the 
crushed  leaves  until  the  condensed  vapor  measures  the  proper 
quantity.  More  rarely  it  is  prepared  by  agitating  a  known 
proportion  of  the  oil  with  distilled  water,  as  is  practised  in  the 
preparation  of  the  aromatic  waters  of  the  Pharmacopoeia. 
In  addition  to  the  above  sources  of  inaccuracy,  there  is  one 
other  which  has  by  no  means  attracted  the  attention  which  the 
importance  of  the  question  seems  to  me  to  deserve.  It  is  this  :  Lie- 
big  and  Wdhler,  though  unable  in  their  analysis  of  laurel-leaves 
to  detect  amygdaline^  concur  in  opinion  as  to  its  existence.  If  this 
be  the  case — and  all  analogy  leads  to  the  inference  that  it  is — the 
well-known  action  by  which  this  body  gives  rise  to  hydrocyanic 
acid  should  surely  not  be  overlooked, asthe  duration  of  the  digestion 
of  the  leaves  in  water,  now  considered  as  a  matter  of  but  secondary. 
