_Hemlock fruits_; F. _Fruits de Ciguë_; G. _Schierlingsfrucht_.
=Botanical Origin=—_Conium maculatum_ L., an erect biennial herbaceous
plant, flourishing by the sides of fields and streams, and in neglected
spots of cultivated ground, throughout temperate Europe and Asia.
It occurs in Asia Minor and the Mediterranean islands, and has been
naturalized in North and South America. But the plant is very unevenly
distributed, and in many districts is entirely wanting. It is found in
most parts of Britain from Kent and Cornwall to the Orkneys.
=History=—Κώνειον, occurring as early as the fourth or fifth century
B.C. in the Greek literature, was the plant under notice, at least in
most cases. The famous hemlock potion of the Greeks by which criminals
were put to death[1145] was essentially composed of the juice of this
plant. The old Roman name of Conium was _Cicuta_; it prevails in the
mediæval Latin literature, but was applied, about 1541, by Gesner
(and probably before him by others) to _Cicuta virosa_ L., another
umbelliferous plant which is altogether wanting in Greece and in
Southern Europe generally, and does not contain any poisonous alkaloid.
To avoid the confusion arising from the same appellation given to
these widely different and quite dissimilar plants, Linnæus, in 1737,
restoring the classical Greek name, called it Conium maculatum.[1146]
Hemlock was used in Anglo-Saxon medicine. It is mentioned as early as
the 1Oth century in the vocabulary of Alfric, archbishop of Canterbury,
as “_Cicuta_, hemlic,”[1147] and also in the Meddygon Myddfai. Hemlock
is derived from the Anglo-Saxon words “hem,” border, shore, and “leác”
leek. Its use in modern medicine is due chiefly to the recommendation
of Störck of Vienna, since whose time (1760) the plant has been
much employed. The extreme uncertainty and even inertness of its
preparations, which had long been known to physicians and had caused
its rejection by many, have been recently investigated by Harley.[1148]
The careful experiments of this physician show what are the real powers
of the drug, and by what method its active properties may be utilized.
=Description=—The fruit has the structure usual to the order; it is
broadly ovoid, somewhat compressed laterally, and constricted towards
the commissure, attenuated towards the apex, which is crowned with a
depressed stylopodium. As met with in the shops, it consists of the
separated mericarps which are about ⅛ of an inch long. The dorsal
surface of these has 5 prominent longitudinal ridges, the edges of
which are marked with little protuberances giving them a jagged or
crenate outline, which is most conspicuous before the fruits are fully
ripe. The furrows are glabrous but slightly wrinkled longitudinally;
they are devoid of vittæ. When a mericarp is cut transversely, the seed
exhibits a reniform outline, due to a deep furrow in the albumen on the
side of the commissure.
[1145] See Imbert-Gourbeyre, _De la mort de Socrate par la Ciguë_,
Paris, 1876.
[1146] An extensive paper has been devoted by Albert Regel to the
_History of Conium_ and _Cicuta_ in the _Bulletin de la Soc. imp. des
Naturalistes de Moscou_, tome li. (1876, first part) 155-203 and lii.
(1877) first part, 1-52.
[1147] _Volume of Vocabularies_, edited by Wright, 1857. 31.
[1148] _Pharm. Journ._ viii. (1867) 460-710; ix. (1868) 53.
The fruits of hemlock are dull greenish grey, and have but little taste
and smell; but when triturated with a solution of caustic alkali they
evolve a strong and offensive odour.
=Microscopic Structure=—Hemlock fruits differ from other fruits of
the order by the absence of vittæ.[1149] In the endocarp, there is a
peculiar layer of small nearly cubic cells surrounding the albumen. The
cells of the endocarp are loaded with a brown liquid consisting chiefly
of conine and essential oil.
=Chemical Composition=—The most important constituent of the fruits of
hemlock _Conine_ or _Conia_, C₈H₁₄NH, a limpid colourless oily fluid,
0·846 sp. gr. at 12°·5 C. It has a strong alkaline reaction, and boils
at 170° C. in an atmosphere devoid of oxygen, without decomposition. It
was first observed by Giseke at Eisleben, Saxony, in 1827, recognized
as an alkaloid by Geiger in 1831, and more amply studied by Wertheim
in 1856 and 1862. To obtain it, an alcoholic extract is submitted
to distillation with a little slaked lime. The product should be
neutralized with oxalic acid, and the oxalate of conine removed by
absolute alcohol mixed with a little ether, oxalate of ammonium being
insoluble. The oxalate of the alkaloid shaken with caustic lye and
ether, affords the conine, on evaporating the solvent and distilling
the alkaloid in a current of dry hydrogen. In the plant it is combined
with an acid (malic?), and accompanied by ammonia, as well as by a
second, less poisonous crystallizable base, called _Conhydrine_,
C₈H₁₇NO, which may be converted into conine by abstraction of the
elements of water. From these alkaloids a liquid non-poisonous
hydrocarbon, _Conylene_, C₈H₁₄, has been separated by Wertheim. Even in
nature one hydrogen atom of conine is frequently replaced by methyl,
CH₃; and commercial conine commonly contains, as shown by A. von Planta
and Kekulé, methyl-conine, C₈H₁₄NCH₃. Lastly there is present in
hemlock fruits a third alkaloid having probably the composition C₇H₁₃N.
As to the yield of conine, it varies according to the development
of the fruits, but it is at best only about ⅕ per cent. According
to Schroff (1870), the fruits are most active just before maturity,
provided they are gathered from the biennial plant. At a later stage,
conine is probably partly transformed into conhydrine, which however is
present in but very small proportion,—about 1¼ per mille at most.
In its deleterious action, conine resembles nicotine, but is much less
powerful.
Schiff (1871-1872) has artificially produced an alkaloid partaking of
the general properties of conine, and having the same composition; but
it is optically indifferent. Conine, on the other hand, we find turns
the plane of polarization to the right.
The fruits of hemlock contain also a volatile oil which appears devoid
of poisonous properties; it exists in but small quantity and has not
yet been fully examined.
[1149] See _Moynier de Villepoix_, _Annales des Sciences naturelles_,
Botanique, v. (1878) 348.
=Uses=—The fruits of hemlock are the only convenient source of the
alkaloid conine. They were introduced into British medicine in 1864,
as a substitute for the dried leaf in making the tincture. But it has
been shown that a tincture, whether of leaf or fruit, is a preparation
of very small value, and that it is far inferior to the preserved juice
of the herb. It has however been pointed out by W. Manlius Smith,[1150]
and his observations have been confirmed by Harley,[1151] that the
_green unripe fruits_ possess more than any other part the peculiar
energies of the plant, and that they may even be dried without loss of
activity. A medicinal fluid extract of considerable power has been made
from them by Squibb of New York.