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.
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.