"Poisons and poisoning" was the subject of a discourse a few days ago
at the Royal Institution. The lecturer, Professor Meymott Tidy, began
by directing attention to the derivation of the word "toxicology," the
science of poisons. The Greek word [Greek: toxon] signified primarily
that specially oriental weapon which we call a bow, but the word in
the earliest authors included in its meaning the arrow shot from the
bow. Dioscorides in the first century A.D. uses the word [Greek: to
toxikon] to signify the poison to smear arrows with. Thus, by giving
an enlarged sense to the word--for words ever strive to keep pace, if
possible, with scientific progress, we get our modern and significant
expression toxicology as the science of poisons and of poisoning. A
certain grim historical interest gathers around the story of poisons.
It is a history worth studying, for poisons have played their part in
history. The "subtil serpent" taught men the power of a poisoned fang.
Poison was in the first instance a simple instrument of open warfare.
Thus, our savage ancestors tipped their arrows with the snake poison
in order to render them more deadly. The use of vegetable extracts for
this purpose belongs to a later period. The suggestion is not
unreasonable that if war chemists with their powders, their gun
cotton, and their explosives had not been invented, warlike nations
would have turned for their _instrumenta belli_ to toxicologists and
their poisons. At any rate, the toxicologists may claim that the very
cradle of science was rocked in the laboratory of the toxicological
worker. Early in the history of arrow tipping the admixture of blood
with the snake poison became a common practice. Even the use of animal
fluids alone is recorded--e.g., the arrows of Hercules, which were
dipped in the gall of the Lernæan hydra. Hercules himself at last fell
a victim to the blood stained tunic of the dead Centaur Nessus. As
late as the middle of the last century Blumenbach persuaded one of his
class to drink 7 oz. of warm bullock's blood in order to disprove the
then popular notion that even fresh blood was a poison. The young man
who consented to drink the blood did not die a martyr to science.
The first important question we have to answer is, What do we mean by
a poison? The law has not defined a poison, although it requires at
times a definition. The popular definition of a poison is "a drug
which destroys life rapidly when taken in small quantity." The terms
"small quantity" as regards amount, and "rapidly" as regards time, are
as indefinite as Hodge's "piece of chalk" as regards size. The
professor defined a poison as "any substance which otherwise than by
the agency of heat or electricity is capable of destroying life,
either by chemical action on the tissues of the living body or by
physiological action by absorption into the living system." This
definition excepted from the list of poisons all agencies that
destroyed life by a simple mechanical action, thus drawing a
distinction between a "poison" and a "destructive thing." It explains
why nitrogen is not a poison and why carbonic acid is, although
neither can support life. This point the lecturer illustrated. A
poison must be capable of destroying life. It was nonsense to talk of
a "deadly poison." If a body be a poison, it is deadly; if it be not
deadly, it is not a poison. Three illustrations of the chemical
actions of poisons were selected. The first was sulphuric acid. Here
the molecular death of the part to which the acid was applied was due
to the tendency of sulphuric acid to combine with water. The stomach
became charred. The molecular death of certain tissues destroyed the
general functional rhythmicity of the system until the disturbance
became general, somatic death (that is, the death of the entire body)
resulting. The second illustration was poisoning by carbonic oxide.
The professor gave an illustrated description of the origin and
properties of the coloring matter of the blood, known as _hæmoglobin_,
drawing attention to its remarkable formation by a higher synthetical
act from the albumenoids in the animal body, and to the circumstance
that, contrary to general rule, both its oxidation and reduction may
be easily effected. It was explained that on this rhythmic action of
oxidizing and reducing _hæmoglobin_ life depended.
Carbonic oxide, like oxygen, combined with _hæmoglobin_, produced a
comparatively stable compound; at any rate, a compound so stable that
it ceased to be the efficient oxygen carrier of normal _hæmoglobin_.
This interference with the ordinary action of _hæmoglobin_ constituted
poisoning by carbonic oxide. In connection with this subject the
lecturer referred to the use of the spectroscope as an analytical
agent, and showed the audience the spectrum of blood extracted from
the hat of the late Mr. Briggs (for the murder of whom Muller was
executed), and this was the first case in which the spectroscopic
appearances of blood formed the subject matter of evidence. The third
illustration of poisoning was poisoning by strychnine. Here again the
power of the drug for undergoing oxidation was illustrated. It was
noted that although our knowledge of the precise _modus operandi_ of
the poison was imperfect, nevertheless that the coincidence of the
first fit in the animal after its exhibition with the formation of
reduced _hæmoglobin_ in the body was important.
There followed upon this view of the chemical action of poison in the
living body this question: Given a knowledge of certain properties of
the elements--for example, their atomic weights, their relative
position according to the periodic law, their spectroscopic character,
and so forth--or given a knowledge of the molecular constitution,
together with the general physical and chemical properties of
compounds--in other words, given such knowledge of the element or
compound as may be learned in a laboratory--does such knowledge afford
us any clew whereby to predicate the probable action of the element or
of the compound respectively on the living body? The researches of
Blake, Rabuteau, Richet, Bouchardat, Fraser, and Crum-Brown were
discussed, the results of their observations being that at present we
were unable to determine toxicity or physiological action by any
general chemical or physical researches. The lecturer pointed out that
such relationship was scarcely to be expected. Poisons acted on
different tissues, while even the same poison, according to the dose
administered and other conditions, expended its toxic activity in
different ways.
Further, the allotropic modifications of elements and the isomerism of
compounds increased the difficulties. Why should yellow phosphorus be
an active poison and red phosphorus be inert? Why should piperine be
the poison of all poisons to keep you awake, and morphine the poison
of all poisons to send you asleep, although to the chemist these two
bodies were of identical composition? The lecturer urged that the
science of medicine (for the poisons of the toxicologist were the
medicines of the physician) must be experimental. Guard jealously
against all wanton cruelty to animals; but to deprive the higher
creation of life and health lest one of the lower creatures should
suffer was the very refinement of cruelty. "Are ye not of much more
value then they?" spoke a still small voice amid the noisy babble of
well intentioned enthusiasts.--_London Times._
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