during first aid treatment of snakebite is not or-
dinarily harmful, but snake venom injected
parenterally is extremely poisonous.
There are various ways in which poisons may
be introduced into the body, the most common
being by mouth, inhalation, and injection.
Poisons taken by mouth enter the circulation
through absorption from the stomach and in-
testine. Those inhaled enter the circulation
through the lungs. When parenterally injected or
deposited into the urethra, rectum, or vagina,
poisons enter the circulation through absorption
from the body tissues in those areas. If the injec-
tion is intravenous, the poisons are directly in-
troduced into the bloodstream. Poisons may also
be introduced by application to open wounds and
to the unbroken skin. After entering the circula-
tion, a poison is carried by the blood to the tissues
and organs susceptible to its action and attacks
Most of the excretion of poisons from the
body occurs in the kidneys, liver, gastrointestinal
tract, and skin. Poisons may be excreted from the
system unchanged or in the form of other com-
pounds into which they have been transformed
by the action of various body organs and tissues.
The most damaging effects of some poisons are
found at the point of excretion.
Various conditions of the individual may
modify the actions and effects of poisons on the
body. The age of the victim makes a great deal
of difference, with young children being more
susceptible to poisons than adults. Conditions
caused by poisons will vary because of a personal
idiosyncrasy; that is to say, some persons by
nature are unusually sensitive to certain poisons,
while others possess a natural tolerance for cer-
tain poisons that is not the result of habitual use.
Through habitual use of certain poisons, espe-
cially narcotics, most persons may become so
accustomed to their effects that they are not
poisoned when taking doses that would ordinarily
prove lethal in the unaddicted. It occasionally hap-
pens, however, that continual external use of
chemical substances results in hypersensitivity.
The actions of poisons may be considerably
modified by disease, some diseases increasing and
others lessening the action of poisons. In the lat-
ter case, large doses are usually required to pro-
duce the desired effect.
Poisoning may either be acute or chronic.
Acute poisoning is the condition brought on by
taking an overdose. Chronic poisoning is the con-
dition brought on by taking repeated doses of a
poison or as the result of the absorption of the
poison over a long period.
CLASSIFICATION OF POISONS
These poisons are present in the gaseous state
and if inhaled, destroy the capability of the blood
as a carrier of oxygen and irritate or destroy the
tissues of the air passages and lungs. When in con-
tact with the skin and mucous membranes,
gaseous poisons produce lacrimation, vesication,
inflammation, and congestion. Examples are car-
bon monoxide, carbon dioxide, hydrogen sulfide,
sulfur dioxide, ammonia gas, chlorine gas, and
chemical warfare agents
Inorganic poisons fall into two classes: (a)
Corrosives, which are substances that rapidly
destroy or decompose the body tissues at point
of contact. Some examples are hydrochloric,
nitric, and sulfuric acids; phenol; sodium hydrox-
ide; and iodine. (b) Metals and their salts, which
are corrosive and irritate locally, but whose chief
action occurs after absorption when they damage
internal organs, especially those of excretion.
Some examples are arsenic, antimony, copper,
iron, lead, mercury, radioactive substances, and
These poisons are nitrogenous plant principles
that produce their chief effect on some part of
the central nervous system. Some examples are
atropine, cocaine, morphine, and strychnine.
These poisons include various chemical com-
pounds, some obtained from plants, having hyp-
notic, neurotic, and systemic effects. Some
examples are barbiturates, salicylates, digoxin,
EFFECTS AND SYMPTOMS OF
For convenience of study, the following
general classification of poisons is based accord-
ing to their effects on the body and the general
symptoms of poisoning.