CLASSIFICATION OF POISONS.
There is nothing more difficult in toxicology than to give a
satisfactory classification of poisons, insomuch that some have fallen
back on the no-classification, or natural history system, and grouped
poisons as mineral, vegetable, and animal, according to their source. In
despair of achieving anything better, a modification of the old and
well-known system is here followed, poisons being classed as Corrosives,
Irritants (Simple and Specific), and Neurotics; the latter group is,
however, further subdivided, something in the same way as that adopted
by Dr. Guy. The group of corrosives should comprehend all which by
contact destroy the bodily textures, and so occasion death. These same
substances, when diluted, may be incapable of destroying the tissues
directly, but may do so by setting up inflammation; these with certain
others having like effects, would form the group of simple irritants.
They kill by virtue of their secondary effects on the constitution. But
some substances, like arsenic, are not only capable of inducing local
inflammations, with their secondary effects, but are also possessed of
certain specific and well marked properties differing in each case.
These are _specific irritants_.
Neurotics comprehend all poisons whose effects are mostly referable to
the nervous system, necessarily a most diverse group, which we are not
yet in a position to minutely analyze. Some, however, act mainly on the
brain, some on the spinal cord, some on certain nerves only, or on the
vasomotor system of nerves; some act it is hardly possible to tell how.
There was an old group of _septic_ poisons; to this might still be
referred certain noxious gases, such as sulphuretted hydrogen; or were
it made to include all poisons acting directly on the blood, it would
include the still more dangerous gas, carbonic oxide.
The following table exhibits these subdivisions, and some of the poisons
contained in each:
{ { Sulphuric.
{ Strong Mineral Acids { Nitric.
{ { Hydrochloric.
{
CORROSIVES. { Vegetable Acid Oxalic.
{
{ Alkalies { Strong Alkalies.
{ { Alkaline Carbonates, &c.
{ The above diluted.
SIMPLE IRRITANTS { Lime.
{ Zinc.
{ Silver, &c.
{ Arsenic.
{ Mercury.
SPECIFIC IRRITANTS { Antimony.
{ Phosphorous.
{ Iodine, &c.
{ Opium.
{ Prussic Acid.
{ Chloroform.
NEUROTICS { Belladonna.
{ Aconite.
{ Strychina.
{ Conium.
{ Tobacco, &c.
_Irritant_ poisons give rise to pain in the stomach and bowels,
faintness and sickness, and purging with tenesmus. The evacuations are
often tinged with blood, the pulse is feeble and irregular, and the skin
cold. Many of the substances of this class from irritating the tissues
with which they come in contact, produce a severe burning sensation in
the mouth and oesophagus, as well as in the stomach. The degree of
local destructive action produced will of course vary in proportion to
the amount of the vehicle with which the noxious agent may be diluted.
Irritants cause death by inducing collapse or convulsions, or by
exciting severe inflammation; or, after a variable interval, by leading
to stricture of the oesophagus. The diseases which most resemble the
action of irritants are, malignant cholera, severe diarrhoea, colic,
gastritis, enteritis, rupture of the stomach or intestines, and
obstruction of the bowels, mechanical or otherwise.
The symptoms of apoplexy, epilepsy, and uraemia bear a resemblance to
those caused by some of the poisons of the neurotic class. Others give
rise to delirum with spectral illusions or convulsions. Sometimes there
is tetanus, sometimes coma or syncope. Diseases of the brain and spinal
cord, likely to be confounded with these, are often very insidious in
their progress, and hence may suddenly give rise to suspicious symptoms.
The history, mode of attack, &c., will generally negative any suspicion
of poisoning.
I.--CORROSIVES.