_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]
[749] These names and the following are also applied to the entire
pods, or even to the plant.
[750] Fig. in Bentley and Trimen, _Med. Plants_, part 13 (1876).
[751] _Hist. Plant._ i. 887.
[752] Tom. viii. (1700) tab. 35, sub nom. _Nāi Corana_.
[753] Flückiger, _Documente zur Geschichte der Pharmacie_, Halle, 1876.
84.
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).
The name _Cowhage_ is Hindustani, and in the modern way is written
_Kiwânch_, which is generally derived from the Sanskrit _Kapi-Kachchu_,
monkey’s itch (Dr. Rice); the corruption into _Cow-itch_ is absurd.
_Mucuna_ is the Brazilian name of another species mentioned in 1648 by
Marcgraf.[755]
=Description=—The pods are 2 to 4 inches long, about ⁴/₁₀ of an inch
wide, and contain 4 to 6 seeds; they are slightly compressed and of a
dark blackish brown. Each valve is furnished with a prominent ridge
running from the apex nearly to the base, and is densely covered with
rigid, pointed, brown hairs, measuring about ⅒ of an inch in length.
The hairs are perfectly straight and easily detached from the valves,
out of the epidermis of which they rise. If incautiously touched, they
enter the skin and occasion an intolerable itching.
=Microscopic Structure=—Under the microscope the hairs are seen to
consist of a single, sharply pointed, conical cell, about ¹/₄₀ of an
inch in diameter at the base, with uniform brownish walls 5 mkm. thick,
which towards the apex are slightly barbed. Occasionally a hair shows
one or two transverse walls. Most of the hairs contain only air; others
show a little granular matter which acquires a greenish hue on addition
of alcoholic solution of perchloride of iron. If moistened with chromic
acid, no structural peculiarity is revealed that calls for remark.
The walls however are somewhat separated into indistinct layers, the
presence of which is confirmed by the refractive power displayed by the
hairs in polarized light.
=Chemical Composition=—The hairs when treated with sulphuric acid and
iodine assume a dark brown colour. Boiling solution of potash does not
considerably swell or alter them. They are completely decolorized by
concentrated nitric acid.
=Uses=—Cowhage is administered for the expulsion of intestinal worms,
especially _Ascaris lumbricoides_ and _A. vermicularis_, which it
effects by reason of its mechanical structure. It is given mixed with
syrup or honey in the form of an electuary.
The root and seeds are reputed medicinal by the natives of some part of
India. The pods when young and tender may be cooked and eaten.
[754] _On the efficacy of Stizolobium or Cowhage_, Lond. 2nd ed. 1784.
[755] _Hist. Nat. Brasil._ 18.