i68 
Chemistry  of  the  Proteins. 
Am.  Jour.  Ph«rm 
April,  1907. 
THE  CHEMISTRY  OF  THE  PROTEINS  AND  THEIR 
RELATION  TO  BIOLOGY.1 
By  Emii,  Fischer. 
It  is  not  surprising  that  substances  of  such  eminent  importance 
as  the  foodstuffs  have  long  been  the  subjects  of  scientific  investiga- 
tion, when  it  is  remembered  that  the  great  majority  of  the  people 
pay  out  more  than  one-half  of  their  incomes  in  purchasing  them. 
Physiology,  chemistry,  botany,  and  medicine  strive  to  establish  their 
value,  their  composition,  their  formation  in  the  plant  world,  and 
their  fate  in  the  animal  kingdom.  Generally  speaking,  foodstuffs 
show  great  similarity  in  chemical  composition,  though  differing 
widely  in  outward  form,  in  color,  taste,  and  smell ;  for  the  great 
majority  consist  of  complicated  compounds  of  carbon,  or  so-called 
organic  substances,  built  up  by  remarkable  synthetic  processes  in 
plants  from  very  simple  materials — namely,  water,  carbon  dioxide, 
nitrates,  and  a  few  other  salts  found  in  the  earth.  These  products 
then  undergo  manifold  changes  in  the  animal  body — sometimes  a 
radical  decomposition  previous  to  being  used  for  the  building  up  of 
the  organs,  and,  finally,  they  are  reconverted  into  the  materials  from 
which  they  were  made — namely,  carbon  dioxide,  water,  etc.  For 
the  correct  interpretation  of  these  changes  it  is  necessary  to  acquire 
an  accurate  knowledge  of  the  chemical  nature  of  each  individual 
substance,  which  occurs  at  any  time  during  the  cycle,  and  this  is 
the  problem  which,  for  the  last  one  hundred  years,  organic  chemistry 
has  tried  to  solve — always  with  increasing  success. 
THREE  GROUPS  OF  FOODSTUFFS. 
The  large  number  of  organic  compounds  which  have  in  this  way 
to  be  considered  may  be  fairly  sharply  divided  into  three  classes — 
the  fats,  the  carbohydrates,  and  the  proteins,  as,  apart  from  water, 
they  form  the  major  portion  of  our  nutriment.  Their  composition 
was  proved,  qualitatively,  in  the  eighteenth  century  by  Lavoisier, 
and,  quantitatively,  with  fair  accuracy,  in  the  beginning  of  the 
nineteenth  century.  But  of  much  more  importance  and  of  greater 
difficulty  to  ascertain  is  their  constitution,  or  the  structure  of  their 
molecules,  and  in  this  respect  our  knowledge  of  the  three  classes 
1  Abstract  of  a  lecture  delivered  before  the  Royal  Prussian  Academy  of 
Sciences  ;  reprinted  from  Pharm.  Jour.,  March  2,  1907,  p.  261. 
