Scraped or decorticated ginger is often bleached, either by being subjected to the fumes of burning sulphur, or by immersion for a short time in solution of chlorinated lime. Much of that seen in the grocers’ shops looks as if it had been whitewashed, and in fact is slightly coated with calcareous matter,—either sulphate or carbonate of calcium.[2363]
Microscopic Structure—A transverse section of coated ginger exhibits a brown, horny external layer, about one millimètre broad, separated by a fine line from the whitish mealy interior portion, through the tissue of which numerous vascular bundles and resin-cells are irregularly scattered. The external tissue consists of a loose outer layer, and an inner composed of tabular cells: these are followed by peculiar short prosenchymatous cells, the walls of which are sinuous on transverse section and partially thickened, imparting a horny appearance. This delicate felted tissue forms the striated surface of scraped ginger, and is the principal seat of the resin and volatile oil, which here fill large spaces. The large-celled parenchyme which succeeds is loaded with starch, and likewise contains numerous masses of resin and drops of oil. The starch granules are irregularly spherical, attaining at the utmost 40 mkm. Certain varieties of ginger, owing to the starch having been rendered gelatinous by scalding, are throughout horny and translucent. The circle of vascular bundles which separates the outer layers and the central portion is narrow, and has the structure of the corresponding circle or nucleus-sheath in turmeric.
Chemical Composition—Ginger contains a volatile oil which is the only constituent of the drug that has hitherto been investigated. By distilling 112 lb. of Jamaica ginger with water in the usual way, we obtained 4½ ounces of this oil, or about ¼ per cent. It is a pale yellow liquid of sp. gr. 0·878, having the peculiar odour of ginger, but not its pungent taste. It dissolves but sparingly in alcohol (0·83); and deviates the ray of polarized light 21°.6 to the left, when examined in a column 50 mm. long. We learn from kind information given us (1878) by Messrs. Schimmel & Co. at Leipzig, that they obtain as much as 2·2 per cent. of oil from good ginger.
The burning taste of ginger is due to a resin which we have not examined, but which well deserves careful analysis. Protocatechuic acid, which is so commonly afforded by resins ([see page 243]), is also produced by melting the resin of ginger with caustic potash, as shown in 1877 by Stenhouse and Groves.
Commerce—Great Britain imported of ginger as follows:—
| 1868 | 1869 | 1870 | 1871 | 1872 |
| 52,194 cwt. | 34,535 cwt. | 33,854 cwt. | 32,723 cwt. | 32,174 cwt. |
In 1876 the imports were 62,164 cwt., valued at £169,252.
The drug was received in 1872 thus:—
| From | Egypt | 4,923 | cwt. |
| ” | Sierra Leone | 6,167 | ” |
| ” | British India | 13,310 | ” |
| ” | British West Indies | 7,543 | ” |
| ” | other countries | 231 | ” |
| Total | 32,174 | ” |
The shipments from Jamaica during the years 1866 to 1876 varied from 599,786 lb. in 1872 to 1,728,075 in 1867. In 1876 there were exported 1,603,764 lb., valued at £28,882.[2364]