Am.  Jour.  Pharm.  \ 
August.  1899.  J 
Detection  of  Blood. 
367 
and  guaiaconic  acid  as  the  oxidable  compound)  small  quantities 
of  the  intensely  blue  colored  oxidation  product  are  formed  gradu- 
ally. It  is  true,  however,  that  the  "  guaiacum  blue,"  especially  in 
the  presence  of  organic  reducing  agents,  is  not  very  stable,  in- 
asmuch as  this  compound,  to  use  an  expression  of  its  first  investi- 
gator, C.  F.  Schbnbein,  contains  loosely  combined,  movable  and  active 
oxygen  in  the  ozonide  state. 
The  foregoing  shows,  as  it  seems,  the  .usefulness  of  the  modified 
guaiacum  blood-test  when  cautiously  applied ;  on  the  other  hand,  it 
cannot  be  denied  that  the  reaction  is  liable  to  certain  misinterpre- 
tations, in  cases  where  some  other  organic  or  inorganic  substances 
are  present,  instead  of  blood.  It  is  scarcely  necessary  to  mention  in 
this  place  the  numerous  compounds  which,  as,  for  instance,  nitrous 
acid,  free  chlorine,  bromine  and  iodine,  chromic  anhydride,  perman- 
ganic acid,  peroxide  of  lead,  the  ferric  and  cupric  salts,  quinone,  etc., 
directly  color  blue  the  guaiacum  resin ;  because,  first  of  all,  many 
of  these  bodies  are  exempted  a  priori  in  the  majority  of  materials 
submitted  to  the  blood-tests,  and  secondly,  because  in  their  presence 
the  liquid  extract  of  a  stain  to  be  tested  for  blood  would  at  once 
strike  a  blue  color  when  mixed  with  a  little  guaiacum  tincture  before 
the  addition  of  Hiinef  eld's  peroxide- solution.  In  regard  to  these  facts, 
the  somewhat  superficial  notice  of  some  text-books,  viz.,  that  the 
guaiacum  blood-test  is  not  reliable,  "because  many  substances  change 
guaiacum  for  themselves,"  cannot  be  taken  as  a  warning  against  the 
use  of  the  said  method,  since,  certainly,  no  careful  analyst  will  ever 
neglect  to  avoid  mistakes  by  availing  himself  of  the  control-reactions 
indicated  in  each  case !  Yet,  such  substances  of  inorganic  or 
organic  origin,  as  share  the  "  ozone-transferring "  quality  with 
the  contents  of  the  blood  cells,  viz.,  the  coloring  matter  of  blood, 
might  in  some  single  cases  lead  to  a  false  interpretation  of  the 
guaiacum-blue-reaction.  Among  organic  vegetable  substances, 
bodies  of  the  class  of  ferments  may  be  named,  as  well  as  hydrolytic 
ferments  (enzymes  in  the  stricter  sense  of  the  word)  chiefly  so- 
called  oxidizing  ferments,  as  they  occur  in  numerous  parts  of  plants, 
especially  in  mushrooms  and  plant  seeds,  while  among  animal  sub- 
stances in  the  first  line  saliva,  extracts  of  some  organs,  the  contents 
of  white  blood  cells  and  pus  cells,  etc.,  show  analogous  properties. 
These  albuminous  substances  of  the  character  of  ferments,  existing 
in  vegetable  and  animal  cells,  and  exerting  in  a  more  or  less  mani- 
