'"jimel'issT™ ■}   Analytical  Researches  and  Investigations.  287 
suspected  spot  is  treated  in  a  suitable  glass  with  a  dilute  solution  of 
potassa.  When  the  coloration  of  the  alkaline  liquid  appears  no  longer 
to  increase  the  liquid  is  poured  off  and  the  fabric  washed  with  water. 
The  obtained  liquids^  which  are  usually  turbid,  are  filtered,  a  solution 
of  tannin  added,  whereby  the  liquid  instantly  assumes  a  deeper  reddish- 
brown  color,  and  then  made  just  perceptibly  acid  with  dilute  acetic 
acid ;  at  once  or  after  some  time  a  more  or  less  colored  precipitate  is 
separated.  The  latter  is  collected  upon  a  filter,  washed  with  water, 
and  two  portions  of  the  same  brought  upon  two  object  glasses.  After 
the  addition  of  a  trace  of  salt  they  are  allowed  to  dry,  and  the  blackish 
residue  treated  in  the  ordinary  way  with  acetic  acid,  in  the  one  case 
with  the  aid  of  heat,  in  the  other  at  the  ordinary  temperature.  After 
standing  quietly  for  some  time,  from  20  to  24  hours,  the  ha^min  crys- 
tals are  sought  first  in  the  preparation  formed  with  the  aid  of  heat 
and  afterwards  in  that  prepared  in  the  cold.  With  the  former  the 
crystals  are  found  on  the  edge  of  the  object  glass,  with  the  latter  in 
the  middle  of  the  object ;  the  last  obtained  result  is  conclusive. 
By  means  of  the  microscopic  examination  the  author  distinguishes 
with  certainty  betw^een  the  blood  of  mammals  (round  blood  corpuscles) 
and  the  blood  of  birds,  etc.  (elliptical  blood  corpuscles  with  nucleus). 
In  no  case  can  one  state,  however,  with  absolute  certitude  whether  a 
blood  stain  proceeds  from  the  blood  of  a  man,  an  ox,  a  horse,  sheep  or 
goat,  and  only  in  rare  cases  can  the  personal  view  be  expressed,  that 
according  to  the  size  and  grouping  of  visible  blood  corpuscles  a  stain 
proceeds  from  the  blood  of  a  sheep  or  a  goat  and  not  from  the  blood 
of  an  animal  with  larger  blood  corpuscles. 
From  the  importance  of  this  statement  the  observations  of  Schmid 
in  the  same  connection  may  be  noted.  The  latter  brings  the  detached 
blood  stain  into  a  watch-glass,  allows  it  to  stand  with  a  few  drops  of  a 
30  per  cent,  potassa  solution  for  from  24  to  48  hours,  brings  it  then 
upon  a  glass  plate,  and,  when  the  potassa  solution  has  acted  sufficiently, 
it  may  be  finely  divided  by  means  of  a  needle.  A  few  drops  of  a 
fresh  30  per  cent,  potassa  solution  were  then  added,  and  about  50  of 
the  isolated  blood  corpuscles  measured  under  the  microscope.  From 
the  result  of  these  tabulated  measurements  Schmid  concludes  as  fol- 
lows :  If  it  l)e  required  of  the  expert  to  state  whether  a  stain  proceeds 
from  the  blood  of  a  man  or  from  that  of  an  animal,  the  first  question 
under  certain  circumstances  may  be  definitely  answered,  the  second, 
however,  only  (conditionally. 
