^ebmaJy^Sr'}     Resins  and  Relations  to  Terpenes.  55 
planting  those  produced  by  nature.  The  vanillin  and  the  indigo 
syntheses,  however,  completely  changed  the  whole  chemical  world 
in  this  respect.  Men  began  to  imitate  nature  in  the  building  up 
of  not  only  the  vegetable,  but  also  the  simple  animal  compounds 
— a  few  enthusiasts  casting  longing  glances  at  the  constitutional 
formulae  of  sugar,  starch  and  cellulose,  while  the  ultrachemical 
investigators  dared  even  to  speak  in  undertones  of  the  structure 
of  the  albumins  and  the  resins.  Then  came  Baeyer's  marvellous 
work  on  mellitic  acid.  His  exhaustive  study  of  this  acid,  which 
began  as  early  as  1867,  was  so  far  reaching  in  its  application 
to  the  ring  compounds  that  it  had  much  to  do  with  final  working  out 
of  the  structural  constitution  of  the  terpene  group. 
There  is  a  universal  feeling,  I  think,  among  those  who  have 
watched  the  development  of  organic  chemistry  during  the  last 
twenty  years,  and  especially  along  phytochemical  lines,  that  in  the 
not  distant  future  all  of  the  more  important  plant  compounds 
will  have  been  products  of  the  laboratory.  That  there  is  ground 
for  such  a  statement  is  borne  out  by  what  has  already  been  done. 
The  investigations  of  Loew,  ButlerofT,  Kiliani,  Emil  Fischer,  and 
Wohl  on  the  carbohydrates  are  so  familiar  to  every  one  that  it  is 
only  necessary  to  briefly  refer  to  them  at  this  time.  The  aldehyde 
condensation  reaction  by  Loew  and  ButlerofT,  the  building  up  of 
the  sugars  by  Kiliani  and  the  down-building  by  Wohl  make  the 
synthesis  of  the  hexoses  an  established  fact  and  the  synthesis  of 
the  bioses  at  least  a  possibility  in  the  near  future. 
The  briefest  phyto-synthetic  review  would  be  incomplete  with- 
out referring  to  the  most  recent  work  of  Emil  Fischer  and  his 
pupils  on  the  so-called  polypeptides.  Here  is  a  group  of  complex 
substances  belonging  to  the  albumins  of  both  the  plant  and  the 
t  animal  world,  a  group  of  compounds  whose  synthesis  has,  until 
recently,  been  regarded  by  many  as  beyond  human  possibility. 
Nevertheless,  Fischer  has  built  up  the  complex  polypeptides  until 
the  artificial  molecules  are  equal  in  size  to  the  albumins  themselves, 
leaving  the  synthesis  of  these  complex  chemical  substances  no 
longer  in  the  list  of  vain  possibilities. 
Of  scarcely  less  importance  in  the  phytochemical  world  than  the 
carbohydrates,  the  alkaloids  and  the  albumins,  are  the  resins  and 
terpenes.  Wallach  has  presented  a  satisfactory  constitutional 
formula  for  pinene,  but  the  resins  are  still  classed  with  substances 
