1. _Cassia acutifolia_ Delile[835]—a shrub about 2 feet high, with
pale subterate or obtusely angled, erect or ascending branches,
occasionally slightly zigzag above, glabrous at least below. Leaves
usually 4-5-jugate; leaflets oval or lanceolate, acute, mucronate,
usually more or less distinctly puberulous or at length glabrous,
pale or subglaucous at least beneath, subsessile. Stipules subulate,
spreading or reflexed, 1-2 lines long. Racemes axilliary, erect, rather
laxly many-flowered, usually considerably exceeding the subtending
leaf. Bracts membranous, ovate or obovate, caducous. Pedicels at length
2-3 lines. Sepals obtuse, membranous. Two of the anterior anthers much
exceeding the rest of the fertile stamens. Legume flat, very broadly
oblong, but slightly curved upwards, obliquely stipitate, broadly
rounded at the extremity with a minute or obsolete mucro indicating the
position of the style on the upper edge; 1½-2¼ inches long, ¾-1 inch
broad; valves chartaceous, obsoletely or thinly puberulous, faintly
transverse-veined, unappendaged. Seeds obovate-cuneate, compressed;
cotyledons plane, extending the large diameter of the seed in
transverse section.[836]
[832] See Yule, _Marco Polo_, ii. (1874). 369.
[833] Some writers have removed these plants from _Cassia_ to a
separate genus named _Senna_, but such subdivision is repudiated by the
principal botanists. The intricate synonymy of the senna plants has
been well worked out by J. B. Batka in his memoir entitled _Monographie
der Cassien-Gruppe Senna_ (Prag, 1866), of which we have made free
use. We have also had the advantage of the recent _Revision of the
Genus Cassia_ by Bentham (_Linn. Trans._, xxvii. 1871. 503) and of
the labours of Oliver on the same subject in his _Flora of Tropical
Africa_, ii. (1871) 268-282.
[834] On the structure of the seed, see Batka, _Pharm. Journ._ ix.
(1850) 30.
[835] _Synonyms_—_C. Senna_ β. Linn.; _C. lanceolata_ Nectoux; _C.
lenitiva_ Bisch.; _Senna acutifolia_ Batka.
[836] We borrow the above description from Prof. Oliver.
The plant is a native of many districts of Nubia (as Sukkot, Mahas,
Dongola, Berber), Kordofan and Sennaar; grows also in Timbuktu and
Sokoto, and is the source of _Alexandrian Senna_.
2. _C. angustifolia_ Vahl[837]—This species is closely related to the
preceding, the general description of which is applicable to it with
the following exceptions. In the present plant the leaflets, which are
usually 5-8-jugate, are narrower, being oval-lanceolate, tapering from
the middle towards the apex; they are larger, being from one to nearly
2 inches long, and are either quite glabrous or furnished with a very
scanty pubescence. The legume is narrower (7-8 lines broad), with the
base of the style distinctly prominent on its upper edge.
The plant abounds in Yemen and Hadramaut in Southern Arabia; it is also
found on the Somali coast, in Sind and the Punjab. In some parts of
India it is now cultivated for medicinal use.
The uncultivated plant of Arabia supplies the so-called _Bombay Senna_
of commerce, the true _Senna Mekki_ of the East. The cultivated and
more luxuriant plant, raised originally from Arabian seeds, furnishes
the _Tinnevelly Senna_ of the drug market.
=History=—According to the elaborate researches of Carl Martius,[838] a
knowledge of senna cannot be traced back earlier than the time of the
Elder Serapion, who flourished in the 9th or 1Oth century; and it is
in fact to the Arabian physicians that the introduction of the drug to
Western Europe is due. Isaac Judæus,[839] who wrote probably about A.D.
850-900 and who was a native of Egypt, mentions senna, the best kind of
which he says is that brought from Mecca.
Senna (as _Ssinen_ or _Ssenen_) is enumerated among the commodities
liable to duty at Acre in Palestine at the close of the 12th
century.[840] In France in 1542, a pound of senna was valued in an
official tariff[841] at 15 sols, the same price as pepper or ginger.
The Arabian and the mediæval physicians of Europe used both the pods
and leaves, preferring however the former. The pods (_Folliculi Sennæ_)
are still employed in some countries.
[837] _Synonyms_—_C. lanceolata_ Roxb.; _C. elongata_ Lem. Lis.; _Senna
officinalis_ Roxb.; _S. angustifolia_ Batka.
[838] _Versuch einer Monographie der Sennesblätter_, Leipz. 1867.
[839] _Opera Omnia_, Lugd. 1515, lib. 2. Practices, c. 39.
[840] _Recueil des Historiens des Croisades, Lois_, ii. (1843) 177.
[841] Fontanon, _Edicts et Ordonnances des Roys de France_, éd. 2, ii.
(1585) 349.
_Cassia obovata_ Coll.[842] was the species first known to botanists,
and it was even cultivated in Italy for medicinal use during the first
half of the 16th century. Hence the term _Italian Senna_ used by
Gerarde and others. In the records of the “Cinque savii alla mercanzia”
at Venice we found an order bearing date 1526 to the effect that Senna
leaves of Tuscany were inadmissible; the same was applied in 1676 to
the drug from Tripoli in Barbaria, that from Cairo being exclusively
permitted.
=Production=—According to Nectoux,[843] whose observations relate to
Nubia at the close of the last century, the peasants make two senna
harvests annually, the first and more abundant being at the termination
of the rains,—that is in September; while the other, which in dry
seasons is almost _nil_, takes place in April.
The gathering consists in simply cutting down the shrubs, and exposing
them on the rocks to the burning sun till completely dry. The drug is
then packed in bags made of palm leaves holding about a quintal each,
and conveyed by camels to Es-souan and Darao, whence it is transported
by water to Cairo. By many travellers it is stated that _Senna jebeli_,
i.e. _mountain senna_ (_C. acutifolia_), finds its way to the ports of
Massowhah and Suakin, and thence to Cairo and Alexandria.
_Cassia obovata_, which is called by the Arabs _Senna baladi_, i.e.
_indigenous_ or _wild senna_, grows in the fields of durra (_Sorghum_)
at Karnak and Luxor, and in the time of Nectoux was held in such small
esteem that it fetched but a quarter the price of the _Senna jebeli_
brought by the caravans of Nubia and the Bisharrin Arabs. It is not now
collected.
=Description=—Three kinds of senna are distinguished in English
commerce:—
1. _Alexandrian Senna_—This is furnished by _Cassia acutifolia_ and
is imported in large bales. It used formerly always to arrive in a
very mixed and dirty state, containing, in addition to leaflets of
senna, a variable proportion of leafstalks and broken twigs, pods and
flowers; besides which there was almost invariably an accompaniment of
the leaves, flowers and fruits of _Solenostemma Argel_ Hayne (p. 220),
not to mention seeds, stones, dust and heterogeneous rubbish. Such a
drug required sifting, fanning and picking, by which most of these
impurities could be separated, leaving only the senna contaminated with
leaves of argel. But Alexandrian Senna has of late been shipped of much
better quality. Some we have recently seen (1872) was, as taken from
the original package, wholly composed of leaflets of _C. acutifolia_ in
a well-preserved condition; and even the lower qualities of senna are
never now contaminated with argel to the extent that was usual a few
years ago.
[842] It is a glaucous shrub with obovate leaflets, broadly rounded and
mucronulate, reniform legume terminated by persistent style, and marked
along the middle of each valve by a series of crest-shaped ridges
corresponding to the seeds. It is more widely distributed in the Nile
region than the other species, and is also found in Sindh and Gujerat
and (naturalized) in the West Indies. Its leaflets (also pods) may
occasionally be picked out of Alexandrian Senna.
[843] _Voyage dans la Haute Egypte ... avec des observations sur les
diverses espèces de Séné qui sont répandues dans le commerce_, Paris,
1808. fol.
The leaflets, the general form of which has already been described (p.
216), are ¾ to 1¼ inches long, rather stiff and brittle, generally a
little incurled at the edges, conspicuously veined, the midrib being
often brown. They are covered with a very short and fine pubescence
which is most dense on the midrib. The leaves have a peculiar opaque,
light yellowish green hue, a somewhat agreeable tea-like odour, and
a mucilaginous, not very marked taste, which however is sickly and
nauseous in a watery infusion.
2. _Arabian Moka, Bombay or East Indian Senna_—This drug is derived
from _Cassia angustifolia_, and is produced in Southern Arabia. It is
shipped from Moka, Aden and other Red Sea ports to Bombay, and thence
reaches Europe.
Arabian senna is usually collected and dried without care, and is
mostly an inferior commodity, fetching in London sometimes as low a
price as ½_d._ to ¼_d._ per lb. Yet so far as we have observed, it is
never adulterated, but consists wholly of senna leaflets, often brown
and decayed, mixed with flowers, pods, and stalks. The leaflets have
the form already described (p. 217); short adpressed hairs are often
visible on their under surface.
3. _Tinnevelly Senna_—Derived from the same species as the last, but
from the plant cultivated in India, and in a state of far greater
luxuriance than it exhibits in the drier regions of Arabia where
it grows wild. It is a very superior and carefully collected drug,
consisting wholly of the leaflets. These are lanceolate, 1 to 2 inches
in length, of a yellowish green on the upper side, of a duller tint on
the under, glabrous or thinly pubescent on the under side with short
adpressed hairs. The leaflets are less rigid in texture than those of
Alexandrian senna, and have a tea-like, rather fragrant smell, with but
little taste.
Tinnevelly senna has of late fallen off in size, and some importations
in 1873 were not distinguishable from Arabian senna, except from having
been more carefully prepared. The drug is generally shipped from
Tuticorin in the extreme south of India.
=Chemical Composition=—The analysis of senna with a view to the
isolation of its active principle has engaged the attention of numerous
chemists, but as yet the results of their labours are not quite
satisfactory.
Ludwig (1864) treated an alcoholic extract of senna with charcoal,
and obtained from the latter by means of boiling alcohol two bitter
principles, _Sennacrol_, soluble in ether, and _Sennapicrin_, not
dissolved by ether.
Dragendorff and Kubly (1866) have shown the active substance of senna
to be a colloid body, easily soluble in water but not in strong
alcohol. When a syrupy aqueous extract of senna is mixed with an equal
volume of alcohol, and the mucilage thus thrown down has been removed,
the addition of a further quantity of alcohol occasions the fall of
a dark brown, almost tasteless, easily alterable substance, which
is indued with purgative properties. It was further shown that this
precipitate was a mixture of calcium and magnesium salts of phosphoric
acid and a peculiar acid. The last named, separated by hydrochloric
acid, has been called _Cathartic Acid_; it is a black substance which
in the mouth is at first insipid, but afterwards tastes acid and
somewhat astringent. In water or strong alcohol it is almost insoluble,
and entirely so in ether or chloroform; but it dissolves in warm dilute
alcohol. From this solution it is precipitable by many acids, but not
by tannic.
Groves[844] in 1868, unaware of the researches of Dragendorff and
Kubly, arrived at similar results as these chemists, and proved
conclusively that a cathartate of ammonia possesses in a concentrated
form the purgative activity of the original drug.
The exactness of the chief facts relative to the solubility in
weak alcohol of the active principle of senna set forth by the
said chemists, was also remarkably supported by the long practical
experience of T. and H. Smith of Edinburgh.[845]
When cathartic acid is boiled with alcohol and hydrochloric acid, it is
resolved into sugar and _Cathartogenic Acid_.
The alcoholic solution from which the cathartates have been separated
contains a yellow colouring matter which was called _Chrysoretin_ by
Bley and Diesel (1849), but identified as _Chrysophan_[846] by Martius,
Batka and others. Dragendorff and Kubly regard the identity of the two
substances as doubtful.
The same alcoholic solution which contains the yellow colouring matter
just described, also holds dissolved a sugar which has been named
_Catharto-mannite_. It forms warty crystals, is not susceptible of
alcoholic fermentation, and does not reduce alkaline cupric tartrate.
The formula assigned to it is C₄₂H₄₄O₃₈.
Senna contains tartaric and oxalic acids with traces of malic acid.
The large amount of ash, 9 to 12 per cent., consisting of earthy and
alkaline carbonates, also indicates the presence of a considerable
quantity of organic acids.
=Commerce=—Alexandrian Senna, the produce of Nubia and the regions
further south, was formerly a monopoly of the Egyptian Government,
the enjoyment of which was granted to individuals in return for a
stipulated payment: hence it was known in continental trade as _Séné de
la palte_, while the depots were termed _paltes_ and those who farmed
the monopoly _paltiers_.[847] All this has long been abolished, and the
trade is now free, the drug being shipped from Alexandria.
Arabian senna is brought into commerce by way of Bombay. The quantity
of senna imported thither from the Red Sea and Aden in the year 1871-72
was 4,195 cwt., and the quantity exported during the same period, 2,180
cwt.[848]
=Uses=—Senna leaves are extensively employed in medicine as a purgative.
=Adulteration=—The principal contamination to which senna is at present
liable arises from the presence of the leaves of _Solenostemma Argel_
Hayne, a plant of the order _Asclepiadeæ_, 2 to 3 feet high, growing in
the arid valleys of Nubia. Whether these leaves are used for the direct
purpose of adulteration, or under the notion of _improving_ the drug,
or in virtue of some custom or prejudice, is not very evident. It is
certain however that druggists have been found who _preferred_ senna
that contained a good percentage of argel.
[844] _Pharm. Journ._ x. (1869) 196.
[845] _Ibid._ 315.
[846] See Art. _Radix Rhei_.
[847] From Italian _appaltare_, to let or farm.
[848] _Statement of the Trade and Navigation of the Presidency of
Bombay for_ 1871-72, pt. ii. 21. 98.
Nectoux, to whom we owe the first exact account of the argel or hárgel
plant,[849] describes it as never gathered with the senna by accident
or carelessness, but always separately. In fact he saw, both at Esneh
and Phile, the original bales of argel as well as those of senna: and
at Boulak near Cairo, at the beginning of the present century, the
argel used to be regularly mixed with senna in the proportion of one to
four.
The leaves of argel after a little practice are very easily recognized;
but their complete separation from senna by hand-picking is a tedious
operation. They are lanceolate, equal at the base, of the same size as
senna leaflets but often larger, of a pallid, opaque, greyish-green,
rigid, thick, rather crumpled, wrinkled and pubescent, not distinctly
veined. They have an unmistakeably bitter taste. The small, white,
star-like flowers, or more often the flower buds, in dense corymbs
are found in plenty in the bales of Alexandrian senna. The slender,
pear-shaped follicles, when mature 1½ inches long, with comose seeds
are less frequent. It has been shown by Christison[850] that argel
leaves administered _per se_ have but a feeble purgative action, though
they occasion griping. It is plain therefore that their admixture with
senna should be deprecated.
The leaves or leaflets of several other plants were formerly mixed
occasionally with senna, as those of the poisonous _Coriaria
myrtifolia_ L., a Mediterranean shrub, of _Colutea arborescens_ L., a
native of Central and Southern Europe, and of the Egyptian _Tephrosia
Apollinea_ Delile. We have never met with any of them.[851]