266  Developments  in  Organic  Compounds.     { Am"jUnUe?i9oiarm* 
Loew  explains  this  by  the  increase  of  reactive  ability  towards  the 
aldehyde  groups  of  the  protoplasm.  This  theory  is  supported  by 
the  observation  that  bodies  with  labile  amido  groups  increase  in 
toxicity  when  a  second  amido  group  is  introduced.  This  decreases, 
however,  when  the  amido  (NH2  — )  group  is  converted  into  an 
imido  ( —  NH)  group.    Thus  the  phenylene  diamines 
7NH2 
C  H  / 
XNH2 
are  more  toxic  than 
XNH2 
toluidin,  also  when  one  H  of  the  amido  group  in  anilin  (C6H5NH0) 
is  replaced  by  an  acid  radical  as  acetyl  (CH3CO)  or  benzoyl 
(C6H5CO)  as  in  acetanilid  (C6H5NHCH3CO)  or  benzanilid 
(C6H5NHC6H5CO)  these  bodies  react  less  readily  than  anilin  with 
aldehydes. 
Our  greatest  difficulty  is  accountable  to  our  fragmentary  knowledge 
of  the  selective  powers  of  the  human  organs  and  tissues,  which 
has  been  only  partially  established  through  histological  staining 
and  toxicological  experiments.  Loew's  views  enlighten  us  only 
upon  certain  groups  of  bodies  which  react  with  aldehydes  and 
amido  groups. 
INFLUENCE  OF  HYDROXYL  GROUPS. 
The  introduction  of  hydroxyl  (  — OH)  groups  in  aliphatic  bodies 
modifies  their  action,  which  decreases  with  their  increase  in  num- 
ber. Thus  the  narcotic  alcohols  and  aldehydes  the  harmless  gly- 
cols, glycerols  and  aldols,  still  more  marked  is  the  change  exemplified 
in  the  polyhydric  alcohols,  as  heptol,  mannitol,  etc.  The  presence 
of  this  group  in  caffeine  practically  destroys  its  effect.  These  groups 
so  affect  the  stability  of  a  compound  that  its  decomposition  in  the 
system  is  readily  effected.  The  replacement  of  one  H  in  the  benzole 
ring  increases  its  reactive  ability  and  convulsive  action,  decreasing 
with  an  increase  in  number,  but  toxic  action  in  another  direction 
increases  accordingly,  from  phenol  (C6H5OH)  to  resorcinol 
■  (C6H4(OH)oi-3.)  to  phloroglucin  (C6H3(OH)3r3'5),  chronic  convul- 
sions result  through  action  upon  the  spinal  cord.    Toxicity  and 
