Action Of Poisons; Classification Of Poisons

=Action of Poisons.=--They may act either locally or only after

absorption into the system.



1. Local Action, as seen in (a) corrosive poisons; (b) irritant

poisons, causing congestion and inflammation of the mucous

membranes--e.g., metallic and vegetable irritants; (c) stimulants or

sedatives to the nerve endings, as aconite, conium, cocaine.



2. Remote Action.--This may be of reflex characte , as seen in the

shock produced by the pain caused by corrosive poisons, or the poison

may exert a special action on certain structures, as belladonna on the

cells of the brain, strychnine on the motor nerve cells of the spinal

cord.



3. In Both Ways.--Certain poisons, as carbolic or oxalic acids, act in

this way.



Age, idiosyncrasy, tolerance, and disease, all exert modifying

influences on the action of a poison. The form in which the poison is

swallowed and the quantity also determine its action. In the gaseous

form, poisons act most rapidly and fatally. When in solution and

injected hypodermically, they also act very rapidly. In the solid form

they act as a rule slowly, and may even set up vomiting, and so may be

entirely ejected by vomiting. Poisons act most energetically when the

stomach is empty. If taken when the stomach already contains food,

solution and absorption may be greatly delayed.



Some poisons are cumulative in their action, and thus, even if

infinitesimal doses be swallowed each day, there is a certain amount of

storage in the tissues (though a certain percentage of the poison is

being constantly eliminated), and at last symptoms of poisoning show

themselves.



=Classification of Poisons.=--As an aid to memory, the following

classification is perhaps the best:





I. Inorganic.



1. Corrosive acids and alkalies, and caustic salts (carbolic and

oxalic acids also).

2. Irritant--practically all the metals and the metalloids (I. Cl.

Br. P.).



II. Organic.



{ Animal--venomous bites, food poisoning, cantharides.

1. Irritant { Vegetable--all strong purgatives, hellebores, savin,

{ yew, ergot, hemlock, laburnum, bryony, etc.



2. Neuronic.



(a) Somniferous--opium and its alkaloids.

(b) Deliriant--belladonna, hyoscyamus, stramonium, cannabis,

cocaine, cocculus, camphor, fungi.

(c) Inebriants--alcohol, ether, chloral, carbolic acid (weak),

benzol, aniline, nitro-glycerine.



3. Sedative or depressant.



(a) Neural--conium, lobelia, tobacco, physostigma.

(b) Cerebral--hydrocyanic acid.

(c) Cardiac--aconite, digitalis, colchicum, veratrum.



4. Excito-motory or convulsives--nux vomica, strychnine.



5. Vulnerants--powdered glass.





III. Asphyxiants.



Poisonous and irrespirable gases.