_Cortex Azadirachtæ_; _Nim Bark_, _Margosa Bark_.
=Botanical Origin=—_Melia indica_ Brandis (_M. Azadirachta_ L.,
_Azadirachta indica_ Juss.), an ornamental tree, 40 to 50 feet high
and attaining a considerable girth,[627] well known throughout India
by its Hindustani name of _Nim_, or by its Portuguese appellation of
_Margosa_.[628] It is much planted in avenues, but occurs wild in the
forests of Southern India, Ceylon and the Malay Archipelago, as far as
Java.[629]
The hard and heavy wood which is so bitter that no insect will attack
it, the medicinal leaves and bark, the fruit which affords an acrid
bitter oil used in medicine and for burning, the gum which exudes from
the stem, and finally a sort of toddy obtained from young trees, cause
the _Nim_ to be regarded as one of the most useful trees of India.
_M. indica_ is often confounded with _M. Azedarach_ L., a native of
China,[630] and probably of India, now widely distributed throughout
the warmer regions of the globe, and not rare even in Sicily and
other parts of the south of Europe. The former has an oval fruit (by
abortion) one-celled and one-seeded, and leaves simply pinnate. The
latter has the fruit five-celled, and leaves bipinnate.
=History=—The tree under the Sanskrit name of _Nimba_ is mentioned
in Susruta, one of the most ancient Hindu medical writings, composed
perhaps about the 10th century of our era.
In common with many other productions of India, it attracted the
notice of Garcia de Orta, physician to the Portuguese viceroy at Goa,
and he published an account of it in his work on drugs in 1563.[631]
Christoval Acosta[632] in 1578 supplied some further details and also a
figure of the tree. The tonic properties of the bark, long recognized
by the native physicians of India, were successively tested by Dr. D.
White of Bombay in the beginning of the present century, and have since
been generally admitted.[633] The drug has a place in the _Pharmacopœia
of India_.
=Description=—The bark in our possession[634] is in coarse fibrous
pieces about ⅕ of an inch thick and 2 to 3 inches wide, slightly
channelled. The suberous coat is rough and cracked, and of a greyish
rusty hue. The inner surface is of a bright buff and has a highly
foliaceous structure. On making a transverse section three distinct
layers may be observed—firstly the suberous coat exhibiting a large
brown parenchyme interwoven with small bands of corky tissue,—secondly
a dark cellular layer, and then the foliaceous liber. The dry bark is
inodorous and has a slightly astringent bitter taste.
[627] Fig. in Bentley and Trimen, _Medic. Plants_, part 27.
[628] From _amargoso_, bitter.
[629] C. De Candolle, in _Monogr. Phanerogamar._ i. (1878) 459.
[630] It is mentioned in Chinese writings dating long prior to the
Christian era.—Bretschneider, _Chinese Botanical Works_, 1870. 12.
[631] _Colloquios dos Simples, &c._, Goa, 1563 _Colloq._ xl. p. 153.
[632] _Tractado de las Drogas y Medicinas de las Indias Orientales_,
Burgos, 1578, cap. 43.
[633] Waring, in _Pharmacopœia of India_, 1868. 443.
[634] We are indebted for it to Mr. Broughton of Ootacamund.
=Microscopic Structure=—The suberous coat consists of numerous
layers of ordinary cork-cells, which cover a layer of nearly cubic
sclerenchymatous cells. This latter however is not always met with,
secondary bands of cork (_rhytidoma_) frequently taking its place. The
liber is commonly built up of strong fibre-bundles traversed by narrow
medullary rays, and transversely separated by bands of parenchymatous
liber tissue. Crystals of oxalate of calcium occur in the parenchyme
more frequently than the small globular starch grains. The structure of
the bark varies considerably according to the gradual development of
the secondary cork-bands.
=Chemical Composition=—Margosa bark was chemically examined in India by
Cornish[635] (1856), who announced it as a source of a bitter alkaloid
to which he gave the name of _Margosine_, but which he obtained only
in minute quantity as a “_double salt of Margosine and Soda_” in long
white needles.
From the bitter oil of the seeds he isolated a substance which he
called _Margosic Acid_, and which he doubted to be capable of affording
crystallizable salts. The composition neither of this acid nor of
margosine is known, nor have the properties of either been investigated.
The small sample of the bark at our disposal only enables us to
add that an infusion produced with perchloride of iron a blackish
precipitate, and that an infusion is not altered by tannic acid or
iodohydrargyrate of potassium. If the inner layers of the bark are
alone exhausted with water, the liquid affords an abundant precipitate
with tannic acid; but if the _entire_ bark is boiled in water, the
tannic matter which it contains will form an insoluble compound with
the bitter principle, and prevent the latter being dissolved. It is
thus evident that to isolate the bitter matter of the bark, it would
be advisable to work on the liber or inner layers alone, which might
readily be done, as they separate easily.
According to the recent researches of Broughton[636] the bitter
principle is an amorphous resin soluble in the usual solvents and in
boiling solutions of fixed alkalis. From the latter it is precipitated
by acids, yet, probably, altered. Broughton ascribed the formula
C₃₆H₅₀O₁₁ to this bitter resin purified by means of bisulphide of
carbon, ether and absolute alcohol; it fused at 92° C. He obtained
moreover a small quantity of a crystallized principle, which he
believed to be a fatty body, yet its melting point of 175° C. is not in
favour of this suggestion.
=Uses=—In India the bark is used as a tonic and antiperiodic, both by
natives and Europeans. Dr. Pulney Andy of Madras has found the leaves
beneficial in small-pox.
[635] _Indian Annals of Medical Science_, Calcutta, iv. (1857) 104.
[636] _Madras Monthly Journ. Med. Science_, quoted in _Pharm. Journ._
June 14, 1873, 992.