Mr. Moodeen Sheriff,[748] who says he has often examined the root of Abrus both fresh and dried, remarks that it is far from abounding in sugar as generally considered;—that it does not possess any sweetness at all until it attains a certain size, and that even then its sweet taste is not always well marked. As it is often mixed in the Indian bazaars with true liquorice, he thinks the latter may have sometimes been mistaken for it.
Microscopic Structure—On a transverse section the bark exhibits some layers of cork-cells, loaded with brown colouring matter, and then, within the middle zone of the bark, a comparatively thick layer of sclerenchymatous tissue. Strong liber-fibres are scattered through the interior of the cortical tissue, but are not distributed so as to form wedge-shaped rays as met with in liquorice. In the latter the sclerenchyme (thick-walled cells) is wanting. These differences are sufficient to distinguish the two roots.
Chemical Composition—The concentrated aqueous infusion of the root of Abrus has a dark brown colour and a somewhat acrid taste accompanied by a faint sweetness. When it is mixed with an alkaline solution of tartrate of copper, red cuprous oxide is deposited after a short time: hence we may infer that the root contains sugar. One drop of hydrochloric or other mineral acid mixed with the infusion produces a very abundant flocculent precipitate, which is soluble in alcohol. If the infusion of Abrus root is mixed with a very little acetic acid, an abundant precipitate is likewise obtained, but is dissolved by an excess. This behaviour is similar to that of glycyrrhizin ([see p. 181]).
Berzelius observed, so long ago as 1827, that the leaves of Abrus contain a sweet principle similar to that of liquorice.
Uses—The root has been used in the place of liquorice, for which it is in our opinion a very bad substitute.
SETÆ MUCUNÆ.
Dolichi pubes vel setæ; Cowhage, Cow-itch[749]; F. Pois à gratter, Pois pouillieux; G. Juckborsten.
Botanical Origin—Mucuna pruriens DC. (Dolichos pruriens L., Stizolobium pruriens Pers., Mucuna prurita Hook.), a lofty climbing plant[750] with large, dark purple papilionaceous flowers, and downy legumes in size and shape not unlike those of a sweet pea, common throughout the tropical regions of both Africa, India and America.
History—The earliest notice we have found of this plant is that of Parkinson, who in his Theater of Plants, published in 1640, names it “Phaseolus siliquâ hirsutâ, the Hairy Kidney-Beane called in Zurrate [Surat] where it groweth, Couhage” It was subsequently described by Ray (1686), who saw the plant raised from West Indian seeds, in the garden of the Hatton family in Holborn.[751] Rheede figured it in the Hortus Malabaricus,[752] and it was also known to Rumphius and the other older botanists. We find it even in the pharmaceutical tariff of the county of Nürnberg, a.d. 1714.[753]
The employment of cowhage as a vermifuge originated in the West Indies, and is quite unknown in the East. In England the drug began to attract attention in the latter part of the last century, when it was strongly recommended by Bancroft in his Natural History of Guiana (1769), and by Chamberlaine, a surgeon of London, who published an essay[754] descriptive of its effects which went through many editions. It was introduced into the Edinburgh Pharmacopœia of 1783, and into the London Pharmacopœia of 1809. At the present day it has been almost discarded from European medicine, but has been allowed a place in the Pharmacopœia of India (1868).