AmAuir;SaruJ' }  Botany  and  Chemistry  of  Essential  Oils.  403 
Carvacrol,  readily  obtained  from  camphor  and  a  constituent  of 
Spanish  hop  oil,  is  isomeric  with  thymol,  but  is  the  ortho-derivative. 
Borneol  camphor  is  supposed  to  be  a  secondary  alcohol,  and  on 
oxidation  yields  camphor,  but  in  the  unsatisfactory  state  ,  of  our 
knowledge  concerning  camphor  little  reliance  can  be  placed  on  this 
formula. 
Cineol,  having  the  same  empirical  composition  as  the  above, 
exists  in  many  oils,  but  has  been  disguised  under  different  names  ; 
it  is  an  anhydro  body  and  is  identical  with  eucalyptol,  cajeputol, 
etc.,  and  is  found  in  the  oils  of  wormseed  and  Lavandula  Spicata. 
/  CH2-CH2 
CH3C(  )CPr 
XCHOH-CH/ 
Borneol  Camphor. 
,  CH2*CH2 
CH3CH/  >CHPr 
XCHOH-CH/ 
Menthol. 
Menthol,  C10H20O — this  body,  so  largely  used  in  pharmacy  nowa- 
days, is  a  secondary  alcohol,  and  on  oxidation  yields  a  ketone, 
which  with  sodium  may  be  again  converted  into  menthol. 
These  bodies,  either  ketones  or  secondary  alcohols,  bear  a  very 
close  relation  to  the  terrenes  and  to  paracymene,  but  their  constitu- 
tion has  not  yet  been  verified  by  their  synthetical  formation,  and 
the  formula  of  camphor  must  be  received  with  very  great  caution. 
We  have  thus  left  a  number  of  the  aliphatic  compounds  and 
phenol  derivatives  of  varied  composition.  I  first  propose  to  take  a 
group  of  bodies  very  closely  related  to  each  other,  which  are 
found  in  many  essential  oils,  but  I  must  again  remind  you  that 
our  knowledge  on  this  subject  is  somewhat  meagre,  and  systematic 
investigation  into  their  constituents  has  only  been  undertaken 
within  the  last  few  years. 
Many  oils  are  omitted  on  account  of  insufficient  data  from  which 
to  generalize. 
The  group  that  I  shall  take  includes  the  aldehydes,  alcohols, 
ketones  and  alkyl  salts — all  related  to  each  other  and  often  found 
in  the  same  plant. 
Of  these  several  have  the  same  empirical  composition  as  the 
