Evening star. [volume] (Washington, D.C.) 1854-1972, 1899-05-27
MARVELLOUS SLEUTHS THESE
How Evidences Of Crime Are Investigated
by Experts
Methods and Means Used by Scientists
In Laboratories I'm Recog-
mixing POfsons.
From Tit-BitS.

Marvellous as Is the skill Of a clever de-
tective who, from thumb-print or a shred
of clothing, tracks criminal and brings
him to justice, his methods are simple and
almost clumsy wher compared with the de-
tecuve work done in the laboratory by the
aid of a few Reagents and test-tubes.
In many cases, where some of the subtler
poisons have been the cause of death, the
analyst has absolutely apparent clue to
start him on his investigation. With irr-
tant poisons, which leave their traces on the
body of the victim, his work Is comparative
~ simple; but with the poisons in favorite
use with criminals there is usually no ply
steal trace whatever, and the quantity of
poison taken into the body is 50 small as to
he incredible.
One-tenth OF a grain of aconitine is sufff-
Gent to cause death, that single ounce
of this deadly drug could remove almost
five regiments of soldiers; ounce of
strychnine would similarly be fatal to near
ly LOCO men; and prussic acid is so terribly
ia tai that it has been known to kill without
even being swallowed if placed in the
mouth.
1t is clear then that the laboratory de-
tectve has very difficult and delicate task
to trace the cause of death when the dose
is so microscopically minute, and when
there is no visible sign in the body to guide
him.
But science makes light of such difficult
ties, and succeeds even if only the 800. 0OO.-
OO0th of ounce of some of these poisons
can be found in the body; and it's processes
are delicate and conclusive as they are
interesting.
In testing for strychuine, the fluid OBJ
tanned from the tissues Is concentrated to a
single drop. Bichromate of potash is added
to this drop, which changes in turn to a
deep blue, violet, purple, crimson and fin
ally to delicate blue, however minute
may be the strychnine in 1t.
The faintest trace of arsenic in the fluid
is equally quick to declare itself. If a piece
of copper-foil is placed in contact with it
the arsenic is deposited in a dark film; or if
gas is generated in the liquid and passed
through red-hot glass tube, similar dark
stain appears in the tube and the arsenic
is detected and imprisoned
If mOrphia is present in the body nitric
acid is the detective employed and a single
drop will convert the fluid into deep GRIM
son. Thus whatever the poison, if only the
minutest trace remains in the body, these
subtle reagents inevitably find it.
Such work as the detection of poisons is
child's play to the clever analyst, his real
difficulty comes when he has to determine
whether a certain dark stain is blood and,
if so, whether or not the blood is human.
Many stains which have the appearance
of blood may be quite innocent in their
character; and it is beyond doubt that in
less scientific days many a man has been
sent to the gallOws on the evidence of stains
man blood.
If. for instance the juice of lemon is al
lowed to dry on a knife-blade, it is impos-
sble for any but a chemist to say that the
resultant stain is not blood: AMI the difficult
~ becomes much greater when it is ques-
ton whether a blOOd-stain is human or ami
NAL in It's origin.
There are many conclusive ways of prov
ing that a stain is blood and not vegetable
or other coloring matter. The most reliable
test is to pour little of the tissue-fluid on
sheet of blottingpaper, and add to 1t tine
ture of guaiacum. If a few drops of perox-
ide of hydrogen be then added the fluid
turns to a dark, sapphire blue.
Similarly, if ammonia be added to the
hui6, its color will be unchanged If blood
be present in it; but If the coloring is of
any other origin. the fluid assumes d new
CoiOr-bue, green, violet, etc, according to
the nature of the source.
The crucial stage comes when the analyst
has TO decide whether the blood is human
or otherwise; and for this purpose he relies
chiefly on the microscope. Under the mi
croScOpe the fluid containing the blood will
be found TO have certain bodies floating in
1t. III these bodies are oval in shape, he
knows at once that the blood may be that
of a fish or 4 bird but ii cannot be human
IT, however, the cOrpuscles are round, he is
equally certain that the blood belongs to
the same class as human blood, although
1t might equally well be that of horse a
dog, or guinea pig.
The analysts only resource now Is to
determine by measuring these microscopic
bodies whether not the blood is really
that of a man; and it is in this exceedingly
delicate operation that his great difficulty
is found. He is, however, quite equal even
to this emergency, and is at last able to
appear in court and swear that the stain on
the prisoners clothing or weapon is really
that of human blood.