Am.  Jour.  Pharru.  \ 
August,  1899.  / 
Detection  of  Blood. 
363 
may  be  conserved  for  an  indefinite  time  as  a  "  corpus  delicti,"  and 
at  every  moment  strikes  a  very  intense  blue  color  by  contact  with 
one  or  another  of  the  liquids  containing  loosely  combined  oxygen, 
provided  that  errors  are  cautiously  avoided  by  check  experiments. 
The  proceeding,  wanting  but  a  short  explanation  in  reference  to  the 
more  explicit  description  in  the  paper  quoted,  chiefly  consists  in 
mixing  the  blood  solution,  obtained  by  extraction  of  blood  stains, 
with  an  alcoholic  solution  of  guaiacum  resin2  (or,  as  it  has  been 
lately  proposed  by  0.  D'bbner,  with  a  similar  but  weaker  solution  of 
guaiaconic  acid),  in  which  case  a  milky  secretion  results  of  the 
previously  dissolved  resin  constituents,  which,  in  these  con- 
ditions, partly  attract,  fix  and  precipitate  at  the  same  time  the 
dissolved  or  suspended  coloring  matter  of  blood  (either  in  the 
state  of  hemoglobin  and  methemoglobin  or  of  hematin).  In 
this  way  a  mechanical  combination  of  the  secreted  resin  with  the 
said  blood  constituents  is  formed,  which  process  reminds  us  in 
some  way  of  the  well-known  method  by  which  some  ferments,  like 
pepsin,  are  secreted  by  means  of  an  indifferent  precipitate  caused  in 
the  ferment  solution  and  afterwards  extracted.  If,  then,  we  separate 
the  precipitated  resin  (or  the  above-mentioned  constituent  acting  as 
reagent)  by  thoroughly  dense  filters  (especially  the  newer  "  hardened 
filters"  of  commerce),  the  hematin  compounds  are  fixed  on  the 
surface  of  the  filter  in  extreme  division  together  with  the  particles 
of  resin.  These  filters,  when  well  protected  from  light  and  air  even 
during  the  filtration  process  and  then  cautiously  dried  in  the 
exsiccator,  may  then  be  conserved  for  any  length  of  time.  But  a 
small  piece  of  them  is  wanted,  to  cause  in  a  few  moments  an  intense 
blue  coloration  in  a  porcelain  dish  or  watch  glass  on  white  paper, 
after  it  has  been  moistened  with  a  little  spirit  of  wine,  and  then 
a  small  quantity  of  Hunefeld's  liquid  (mixture  of  so-called 
"  ozonized "  turpentine  oil  with  alcohol,  chloroform  and  a  little 
acetic  acid)  has  been  added.  This  process  is  equally  applicable  to 
blood  stains,  and  to  the  detection  of  blood  in  urine,  and  other  simi- 
lar objects,  and  may  be  used  as  well  for  the  research  of  relatively 
fresh  blood,  as  for  that  of  old  dry  stains,  owing  to  the  fact  already 
2  It  is  preferable,  in  this  case,  to  use  a  solution  of  about  5  per  cent,  of  resin 
(instead  of  the  alcoholic  guaiacum  tincture  ( 1  to  2  per  cent.)  mentioned  by 
Schdnbein  as  the  common  reagent),  in  order  to  secure  an  easy  secretion  of  resin 
in  presence  of  small  portions  of  blood. 
