_Flores Brayeræ_, _Cusso_, _Kousso_, _Kosso_.
=Botanical Origin=—_Hagenia abyssinica_ Willd. (_Brayera
anthelminthica_ Kunth), a handsome tree growing to a height of 60 feet,
found throughout the entire table-land of Abyssinia at an elevation of
3,000 to 8,000 feet above the sea-level.[976] We have never noticed
it growing in any botanic garden. The tree[977] is remarkable for its
abundant foliage and fine panicles of flowers, and is generally planted
about the Abyssinian villages.
[975] _Dispensatory_, 1842. 592.
[976] The French section of the International African Association
contributed Kousso from _Madagascar_ to the Paris Exhibition of 1878.
[977] Fig. in Bentley and Trimen, _Med. Plants_, part 5 (1876).
=History=—The celebrated Bruce[978] during his journey to discover
the source of the Nile, 1768-1773, found the koso tree in Abyssinia,
observed the uses made of it by the natives, and published a figure
of it in the narrative of his travels. It was also described in 1799
by Willdenow who called it _Hagenia_ in honour of Dr. K. G. Hagen of
Königsberg.
The anthelmintic virtues of koso were investigated by Brayer, a French
physician of Constantinople, to which place parcels of the drug are
occasionally brought by way of Egypt, and he published a small pamphlet
on the subject.[979] Several scattered notices of koso appeared in
1839-41, but no supply of it reached Europe until about 1850, when a
Frenchman who had been in Abyssinia obtained a large stock (1,400 lb.,
it was said), a portion of which he endeavoured to sell in London at
35_s._ _per ounce_! The absurd value set upon the drug produced the
usual result: large quantities were imported, and the price gradually
fell to 3_s._ or 4_s._ per lb. Koso was admitted a place in the British
Pharmacopœia of 1864.
=Description=—The flowers grow in broad panicles, 10 to 12 inches in
length. They are unisexual, but though male and female occur on the
same tree, the latter are chiefly collected. The panicles are either
loosely dried, often including a portion of stalk and sometimes a leaf,
or they are made into cylindrical rolls, kept in form by transverse
ligatures. Very often the panicles arrive quite broken up, and with
the flowers in a very fragmentary state. They have a herby, somewhat
tea-like smell, and a bitterish acrid taste.
The panicle consists of a zigzag stalk, which with its many branches
is clothed with shaggy simple hairs, and also dotted over with minute
stalked glands; it is provided at each ramification with a large
sheathing bract. At the base of each flower are two or three rounded
veiny membranous bracts, between which is the turbinate hairy calyx,
having ten sepals arranged in a double series. In the male, the outer
series consists of much smaller sepals than the inner; in the female,
the outer in the ultimate development become enlarged, obovate and
spreading, so that the whole flower measures fully ½ an inch across.
In both, the sepals are veiny and leaf-like. The petals are minute and
linear, inserted with the stamens in the throat of the calyx. These
latter are 10 to 25 in number, with anthers in the female flower,
effete. The carpels are two, included in the calycinal tube; and each
surmounted by a hairy style. The fruit is an obovate one-seeded nut.
Koso as seen in commerce has a light brown hue, with a reddish tinge
in the case of the female flowers, so that panicles of the latter are
sometimes distinguished as _Red Koso_.
[978] Travels, v. (1790) 73.
[979] _Notice sur une nouvelle plante de la famille des Rosacées,
employée contre le Tænia_, Paris, 1822. The reader should also consult
the excellent notice by Pereira written when the drug was first
offered for sale in London. _Pharm. Journ._ x. (1851) 15; reprinted
in Pereira’s _Elem. of Mat. Med._ ii. part 2 (1853) 1815.—Also
Meyer-Ahrens, _Die Blüthen des Kossobaumes_, Zürich, 1851. 90 pp.
=Chemical Composition=—Wittstein (1840) found in koso, together with
the substances common to most vegetables (wax, sugar, and gum), 24 per
cent. of tannin, and 6·25 of an acrid bitter resin, which was observed
by Harms (1857) to possess acid properties.
The researches of Pavesi (1858), and still more those of Bedall[980]
have made us acquainted with the active principle of the drug, which
has been named _Koussin_ or _Kosin_. It may be obtained by mixing the
flowers with lime, exhausting them with alcohol and then with water;
the solutions mixed, concentrated, and treated with acetic acid,
deposit the kosin. We are indebted to Dr. Bedall for a specimen of it,
which we find to consist chiefly of an amorphous, resinoid substance,
from which we got a few yellow crystals by means of glacial acetic acid.
Mr. Merck favoured us with kosin prepared in his laboratory at
Darmstadt. It is a tasteless substance of a yellow colour, forming fine
crystals of the rhombic system,—readily soluble in benzol, bisulphide
of carbon, chloroform or ether, less freely in glacial acetic acid,
and insoluble in water. We found a solution of kosin in 20 parts of
chloroform to be destitute of rotatory power. Of alcohol, sp. gr.
0·818, 1000 parts dissolve at 12° C. only 2·3 parts of this kosin.
It is abundantly soluble in alkalis, caustic or carbonated, yet has
nevertheless no acid reaction, and may be precipitated from these
solutions by an acid without having undergone any alteration. It is
then however a white amorphous mass, which yields the original yellow
crystals by re-solution in boiling alcohol, in which it dissolves
readily. The analysis which we have performed of kosin assigns it the
formula C₃₁H₃₈O₁₀.
Kosin fuses at 142° C., and remains after cooling an amorphous,
transparent yellow mass; but if touched with alcohol, it immediately
assumes the form of stellate tufts of crystals. This may be repeated at
pleasure, kosin not being altered by cautious fusion.
Kosin is not decomposed by boiling dilute acids. It dissolves in strong
sulphuric acid, giving a yellow solution which becomes turbid by the
addition of water, white amorphous kosin being thrown down. At the
same time a well-marked odour exactly like that of Locust Beans, due
to isobutyric acid, CH₃·CH₃·CH·COOH, is evolved. It would thus appear
that in all probability kosin is a compound ether of that acid. It is
very remarkable that the active principle of fern root, the filicic
acid (see Rhizoma Filicis), by decomposition yields butyric acid. If
the sulphuric solution of kosin is allowed to stand for a week, it
gradually assumes a fine red; and then yields, on addition of much
water, an amorphous red mass which after drying is not soluble in
bisulphide of carbon, and may thus be purified. We have not succeeded
in obtaining this red derivative of kosin in a crystalline state.[981]
In its anthelmintic action, kosin is nearly allied with filicic
acid.[982]
Distillation with water separates from the flowers of koso a
stearoptene-like oil having the odour of koso, and traces of valerianic
and acetic acid. No such body as the _Hagenic Acid_ of Viale and Latini
(1852) could be detected by Bedall.
=Commerce=—Koso is brought to England by way of Aden or Bombay; some
appears also to reach Leghorn, probably carried thither direct from
Egypt.
[980] Wittstein’s _Vierteljahresschrift für prakt. Pharm._ viii. (1859)
481; xi. (1862) 207.
[981] Flückiger and Buri, _Yearbook of Ph._ 1875. 19.
[982] Buchheim, _Archiv der Pharmacie, 208_ (1876) 417.
=Uses=—The drug is employed solely as a vermifuge, and is effectual for
the expulsion both of _Tænia solium_ and of _Bothriocephalus latus_.
The Abyssinian practice is to administer the flowers in substance in
a very ample dose, which is sometimes attended with alarming and even
fatal results.
The notion that the action of the drug is partially mechanical and
due to the hairs of the plant, prevails in England, and has led to
the use of an _unstrained_ infusion of the coarsely powdered flowers.
This remedy, from the quantity of branny powder (2 to 4 drachms) that
has to be swallowed, is far from agreeable; and as it occasions strong
purgation and sometimes vomiting, it is not often prescribed.[983]
The fruit of the koso tree, a small indehiscent achene, is stated by
M. Th. von Heuglin[984] to act even more powerful than the flowers;
he calls it (or the seed?) Kosála. It would appear that the fruits
have been used as an anthelmintic two centuries ago in Abyssinia.[985]
Dragendorff (1878) found them to be rich in fatty matters, but devoid
of an alkaloid.