ArebSy,Pi9ai3m'}     Resins  and  Relations  to  Ter  penes.  57 
ship  between  the  resins  and  terpenes.  What  evidence  there  is  may 
be  briefly  stated.  The  fact  that  the  aldehydes  in  the  presence 
of  alkalies  change  to  resinous  matter  was  presented  by  Wiesner 
in  what  may  be  called  the  reduction  theory.  Wiesner 3  assumed 
that  the  resins  are  formed  from  the  carbohydrates,  or,  speaking 
more  specifically,  from  the  starches  by  a  process  of  polymeriza- 
tion and  reduction.  It  is  perfectly  evident  that  Wiesner's  theory 
is  not  applicable  in  all  cases.  The  pine  family,  for  instance,  con- 
tains a  minimum  amount  of  starch,  yet  it  is  the  richest  of  the 
resinous  species.  Wiesner  was  aware  of  this  fact  and  assumed 
that  in  the  case  of  the  pine  family  the  resins  were  formed  through 
the  action  of  gallic  and  gallo-tannic  acids. 
While  the  starch  theory  has  certain  facts  in  its  favor,  there 
are,  on  the  contrary,  serious  objections  to  it.  It  would  seem  not 
only  strange,  but  also  diametrically  opposed  to  general  chemical 
laws,  that  plants  should  proceed  to  build  up  the  complex  starch 
molecule  and  then  break  it  down  again  into  the  resin  and  finally 
into  the  terpene  molecule.  Of  course,  it  must  not  be  forgotten 
that  the  sugars  belong  to  the  aldehydes  and  tend  to  form  resinous 
substances  when  treated  with  alkalies.  They  are,  however,  by  no 
means  as  readily  converted  into  the  resins  as  the  simpler  aldehydes. 
One  would  naturally  expect  that  if  the  resins  are  formed  by  the 
aldehyde  reaction  they  would  proceed  from  the  simple  rather  than 
from  the  complex  aldehydes  or  sugars. 
One  of  the  first  comprehensive  works  on  the  formation  of  the 
resins  from  the  aldehydes  was  presented  by  Baeyer.  He  obtained 
several  synthetic  resins  by  the  aldehyde  condensation  reaction, 
but  an  examination  showed  that  they  were  unlike  any  of  the 
resins  found  in  nature.  In  each  case  the  molecule  seemed  to  be 
extremely  complex  and  no  attempts  were  made  to  determine  the 
structure  or  the  size  of  the  molecule.  Kronstein,  following  out 
the  work  which  Baeyer  had  begun,  presented  constitutional  formulae 
for  these  aldehyde  resins  in  a  very  unique  but  entirely  empirical 
way.  He  assumed  the  resin  molecule  to  be  a  complex  benzene 
ring  or  perhaps  several  superimposed  rings  joined  with  either 
hydrocarbon,  methoxyl,  ethoxyl  or  carboxyl  radicles,  and  gave  the 
graphic  formulae  for  them.    Of  course  such  structural  formulae 
3  Centr.,  1865,  p.  756. 
