Am.  Jour.  Pliarra.  \ 
November,  1904.  / 
Theory  of  Indicators,  etc. 
517 
nitrogenous  bodies.  Kiihne,  Chittenden,  Hofmeister,  Kossel  and 
their  students,  as  well  as  numerous  other  investigators,  have 
attempted  to  arrive  at  a  clear  understanding  of  the  way  in  which 
the  molecule  is  built  up,  breaking  it  down  by  means  of  various 
reagents  until  simple,  readily  recognized  bodies  were  obtained  ;  and 
estimating  the  proportions  of  such  bodies  with  a  view  to  arranging 
a  possible  molecular  complex  which  would  include  them  all. 
Fischer,  on  the  other  hand,  has  devoted  his  attention  principally  to 
the  problem  of  synthetically  producing  bodies  possessing  the  char- 
acteristics of  proteids  from  their  elements  by  building  them  up, 
principally  through  condensation  of  amines  of  the  type  of  glycocol 
and  its  derivative  glycyl-glycin,  the  resulting  bodies  possessing 
properties  very  similar  to  those  of  the  natural  peptones.  Osborne 
has  separated  pure  specimens  of  a  large  number  of  these  nitrogen- 
ous compounds  derived  from  the  proteids,  but  possessed  of  a  simpler 
complex,  and  yet  far  more  complicated  than  the  final  products  of 
disintegration  (leucin,  tyrosin,  etc.),  and  by  preparing  the  hydro- 
chloric acid  salts  of  such  bodies  as  edestin,  arrived  at  conclusions 
regarding  the  probable  molecular  weight. 
Paal  was  the  first  who  attempted  to  throw  light  on  the  nature  of 
the  proteids,  albumoses  and  peptones  by  preparing  the  compounds 
which  they  form  with  bases  and  acids.  By  analyzing  the  prepara- 
tions obtained  in  this  way  at  various  stages  of  digestion  this  inves- 
tigator attempted  to  draw  conclusions  not  only  regarding  the 
absolute  size  of  the  molecules  of  the  various  compounds  isolated, 
but  also  regarding  the  various  more  or  less  resistant  portions  of  the 
original  proteid  molecule  subjected  to  hydrolysis.  Paal  observed 
that  hydrolysis  of  a  complex  molecule  to  form  two  simpler  mole- 
cules, indicated  by  the  increase  in  osmotic  pressure  of  the  mixture, 
was  generally  associated  with  an  equivalent  increase  in  the  ability  to 
take  up  hydrochloric  acid.  This  indicates  the  probable  liberation 
of  an  NH2  group  in  the  ordinary  process  of  hydrolysis.  It  appears, 
however,  extremely  probable  that  by  means  of  suitable  indicators  it 
should  be  possible  to  estimate  not  only  the  total  number  of  such 
NH2  groups  present  in  the  molecule,  but  also  to  differentiate 
between  the  different  types  that  may  possibly  be  formed  vary- 
ing from  those  possessed  of  extremely  basic  to  those  possessed 
of  almost  neutral  or  even  acid  characteristics.  In  a  recent 
publication  dealing  with  the  products  of  decomposition  of  certain 
