_Baryta_, like lime, is a solid, heavy, alkaline earth, having an acrid
and peculiar taste; and turning the syrup of violets _green_, and the
juice of turmeric _red_. When perfectly calcined, it absorbs water very
rapidly, disengaging at the same time a quantity of caloric; the
phenomenon is similar to that of _slacking lime_, and admits of the same
explanation. It dissolves in about 20 parts of water, at the temperature
of 60°; but boiling water will dissolve half its weight of this earth,
part of which will crystallize on cooling.
MURIATE OF BARYTA. This salt crystallises in square plates, or
four-sided prisms; its taste is acrid and pungent. It dissolves in 2½
parts of distilled water at 60° _Fah._ The solution is limpid and
colourless, and has been employed in medicine, as a remedy in scrofula,
cancer, some forms of syphilis, and in hectic fever connected with
ulceration. _Dr. Johnstone_ says that he has seen a delicate female take
as much as thirty drops of a saturated solution of this salt,
_repeatedly_, without nausea; whence he concludes that it would require
at least 2 or 3 drachms to do mischief.[333]
_Symptoms of poisoning by Baryta._
All the soluble compounds of this earth are poisonous, especially the
_muriate_; which, whether injected into the veins, introduced into the
stomach, or externally applied to an abraded surface, will occasion
death in a very short period. We are not aware that any case stands
recorded of poisoning by baryta. _Orfila_[334] and _Brodie_[335] have,
however, investigated the symptoms which this poison produces on
animals, and they appear to be analogous to those occasioned by the
ingestion of arsenic. The muriate, on account of its greater solubility,
would appear to be much more active than the pure earth, or its
carbonate.
_Physiological action of Baryta._
Barytic poisons require to be absorbed before they act on the system;
they may therefore destroy by external application, although it would
appear that, unlike arsenic, they act sooner when internally
administered. _Mr. Brodie_ thinks that the _muriate of baryta_ occasions
death by acting upon the brain and the heart; at the same time it exerts
a local action, and corrodes the viscus with which it comes into
contact.
_Antidotes._
It has been shewn by the experiments of _Orfila_, that the soluble
sulphates, as _Glauber_ or _Epsom salts_, by converting the _baryta_
into an insoluble _sulphate_, will act as antidotes to its virulence. In
the first instance, therefore, it will be prudent to produce this
chemical decomposition in the poison, and then to expel it, as quickly
as possible, by emetics.
_Chemical tests for the detection of Baryta._
Where the pure earth, _baryta_, or its solution in water, is presented
for our investigation, it may be identified by the following reagents.
(_a_) _Sulphuric acid, and the soluble sulphates._ These bodies
precipitate from the barytic solution, a white _sulphate_ of the earth,
insoluble in water, and nitric acid.
(_b_) _Carbonic acid gas, and the alkaline sub-carbonates_, produce in
it a white _carbonate of baryta_.
(_c_) _Muriatic acid_ combines with baryta, and furnishes a salt which
is capable of being identified by numerous reagents. _M. Orfila_ has
furnished us with the following satisfactory compendium of its
habitudes. “A salt which does not redden the tincture of tournesol,
which does not turn the syrup of violets green, which is not
precipitated by the alkaline hydro-sulphurets,[336] nor by ammonia; but
which, on the contrary, is precipitated by the sub-carbonate of ammonia,
soda, or potass; which is not soluble in concentrated alcohol; which
furnishes, with the sulphate of potass, or the sulphuric acid, a white
precipitate insoluble in water and in the nitric acid, and which gives
with the nitrate of silver a curdled precipitate of muriate of silver,
likewise insoluble in the nitric acid, _can be no other than the muriate
of baryta_.”
But it may happen, that the above salt is so mixed with alimentary
matter, as to defy the action of the tests; in this case we must
endeavour to obtain from it the pure earth, by precipitating the
suspected fluids by the sub-carbonate of ammonia; when a _carbonate of
baryta_ will fall down, which must be dried on a filter, and calcined
with charcoal.
CANTHARIDES. _Spanish Flies_—_Blistering Flies_. (_Cantharis
Vesicatoria_, Sp. 1, of Latreille.)[337]
Cantharides are imported into this country in their entire state, and
are so kept in the shops; their form and general appearance are too well
known to require description, and they will rarely become the objects of
inquiry; in powder, however, they may be presented to us for
investigation, and it is therefore essential that the forensic physician
should be acquainted with the appearances which they assume in the state
of disintegration. This powder has a greenish colour, tinged with grey,
and abounding with shining points of a very beautiful green colour, and
which may be recognised in whatever state of division the powder may
exist, even after it has passed through a silken sieve. Its odour is
acrid and nauseous; when thrown on burning coals it emits that peculiar
smell, which generally attends the destruction of animal matter by heat.
The chemical history of _cantharides_ is still involved in some
obscurity; according to _Robiquet_, who has furnished us with the most
satisfactory analysis, they contain various fatty principles; the
phosphates of lime, and magnesia; and the acetic and uric acids;
together with a peculiar crystalline principle, in which the vesicatory
properties wholly reside, and to which the name of _cantharidin_ has
been given by _Dr. Thomson_.[338] It may be obtained in plates, having a
micaceous lustre; when perfectly pure it is insoluble in water, but it
is rendered soluble in that fluid, by the presence of a yellow matter
which exists in native combination with it; it is very soluble in oils.
_Symptoms of poisoning by Cantharides._
As this substance forms an article of the materia medica it may become
an accidental source of poisoning; whilst a general belief in its
aphrodisiac powers may induce a trial of its efficacy, to goad the
exertions of exhausted nature, or to incense the passion of females,
whose seduction is meditated. In the annals of crime in this country, we
are acquainted with but few instances in which cantharides have been
given with the view of destroying life; we have already referred[339] to
the case of _Vaux_, who was executed for poisoning with cantharides;
there is also that of _Sir Thomas Overbury_, who, on the confession of
the person who gave it to him, is said to have taken it, mixed with his
sauces. Cantharides may be administered in the form of powder, infusion,
or tincture. The following may be considered the more prominent symptoms
which will follow the ingestion of a large dose. Violent retching;
copious alvine evacuations, frequently bloody; very severe colics;
active inflammation of the stomach and intestines; sometimes universal
convulsions, attended with a horror of liquids, resembling that which
occurs in hydrophobia; furious delirium, &c. But the affections of the
urinary passages, and organs of generation, may be regarded, κατεξοχην,
as the peculiar symptoms of poisoning by cantharides; such as heat in
the bladder, bloody micturition; horrible strangury; painful and
obstinate priapism; _satyriasis_, &c. If the dose has not been
sufficient to occasion speedy death, it may produce marasmus.
_Organic lesions discovered on dissection._
Where the poison has been administered internally, we shall find the
stomach and intestines presenting an appearance of inflammation, very
similar to that which we have described as the general result of
corrosive poisons. Marks of inflammatory action, and sometimes
ulceration, will be also discovered in the urinary and genital organs;
especially in those cases where the person dies shortly after the
ingestion of the poison.
_Methods of detecting the presence of Cantharides._
Where the poison has been administered in substance, we shall generally
discover some of its particles mixed with the ejected matter; or, after
death, adhering to the coats of the stomach, or to the folds of the
intestines, and which may be easily identified by their peculiar green
and brilliant hue. If the poison should have been administered in the
form of infusion, or tincture, our chemical resources will fail us, and
we must rely alone upon the evidence furnished by the symptoms, and
organic lesions.