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444J                                              MEDICAL' JURISPRUDENCE

The Chemical'Examiner or his - assistant who receives the articles for
analysis from medical officers first verifies the seals, and compares the labels
with the invoice list of the materials sent, and then opens the bottles, etc.
He then places the contents in separate shallow porcelain basins after weigh-
ing and measuring them according to the nature of the material.

A careful inspection of the contents of the stomach and its mucous
membrane is now made both with the naked eye and with a hand-magnifying
lens, making a note of the colour and reaction of the contents. Any foreign
substances, such as particles of undissolved poisons and fragments of seeds,
leaves, roots, etc. of poisonous plants, are next picked up and examined on
a slide under the microscope. The inner wall of the stomach is then washed
with distilled water, and the washings added to the contents. A little of the
stomach contents may be taken on a slide, rubbed up with a drop or two of
glycerin, and when examined under the microscope, may show fragments of
dhatura seeds or Ihang leaves.

For chemical analysis the contents of the stomach are diluted with water,
and the solid viscera are finely chopped up and macerated in water. If the
Chemical Examiner has any clue or indication of the nature of the poison,
he begins by_ searching for it. If not, he usually divides the mixture into
three, parts for the examination of volatile, vegetable and metallic poisons.

1. Volatile Poisons.—Volatile poisons, such as alcohol, ether, hydro-
cyanic acid, benzene, nitro-benzene, aniline, carbolic acid, bromine, iodine and
phosphorus, are separated by distilling the first portion of the mixture
acidulated with tartaric acid, but to separate ammonia, nicotine and volatile
bases the mixture has to be rendered alkaline by the addition of magnesia.
The distillate is then examined for the presence of these poisons by applying
distinctive tests for each.

- 2. Vegetable Poisons.—The detection of vegetable poisons depends on
the isolation of their alkaloids and glucosides from the stomach contents or
organs of the "body and the suspected articles of food, and their identification
by the application of chemical and physiological- tests.

These alkaloids may be grouped under three heads: (1) those derived
from pyridine, e.g. atropine, coniine, (2) those derived from quinoline, e.g.
cinchonine, narcotine, and (3) substituted amines and amides. Mo3t of the
vegetable alkaloids belong to the first two groups. They are mostly solid,
crystalline and colourless, Except a few such as coniine, nicotine and pilo-
carpine, which are liquid. They are insoluble in water, but soluble in ether,
while with acids they form'salts, which dissolve in water, but not in ether.
This fact of solubility is made use of in separating them from organic
mixtures for which the following processes are adopted:—

A. Stas-Otto Process as modified by Autenrieth.—The second paft of
the original mixture is put in a glass flask, acidulated with the addition of
twenty to thirty drops of ten per cent of tartaric acid and digested with tvtf-b
to three times its weight of absolute alcohol. The mixture is heated for a
period of ten to fifteen mintites-on a water bath with a'reflux condenser
attached. It is then cooled and filtered to remove'fat. The residue is then
extracted with alcohol. The filtrates are combined, evaporated in a shallow
porcelain dish to a thin syrupy consistence and mixed with 100 cc. of water.
An abundant precipitate of fat and resinous matter is removed by filtration/
The filtrate is then evaporated to a thick syrupy consistence and extracted
again with absolute alcohol. The alcoholic extract is evaporated and the
residue is dissolved in §0 ec.,of ^ater.. The soiutiorji now contains alkaloidal
tartrafes and may be extracted with,* the- undermentioned- immiscible
solvents i—                                   «         / .. . * t *