ALGÆ (FLORIDEÆ).
CHONDRUS CRISPUS.
Fucus Hibernicus; Carrageen,[2770] Irish Moss; F. Mousse d’Irlande, Mousse perlée; G. Knorpeltang, Irländisches Moos, Perlmoos.
Botanical Origin—Chondrus crispus Lyngbye (Fucus crispus L.), a sea weed of the class Florideæ, abundant on rocky sea-shores of Europe from the North Cape to Gibraltar; not frequent however in the Baltic, and altogether wanting in the Mediterranean, but largely met with on the eastern coasts of North America.
History—Chondrus crispus was figured in 1699 by Morison,[2771] yet only Todhunter at Dublin introduced it to the notice of the medical profession in England in 1831, and shortly afterwards it attracted some attention in Germany. It was never admitted to the London or British pharmacopœia, and is but little esteemed in medicine.
Description—The entire plant is collected: in the fresh state it is soft and cartilaginous, varying in colour from yellowish-green to livid purple or purplish-brown, but becoming, after washing and exposure to the sun, white or yellowish, and when dry, shrunken, horny and translucent.
The base is a small flattened disc, from which springs a frond or thallus 4 to 6 inches or more in length, having a slender subcylindrical stem, expanding fan-like into wedge-shaped segments, of very variable breadth, flat or curled, and truncate, emarginate or bifid at the summit.
The fructification[2772] consists of tetraspores or cystocarps, rising but slightly from the substance of the thallus, and appearing as little wart-like protuberances.
In cold water, carrageen swells up to its original bulk, and acquires a distinct seaweed-like smell. A quantity of water equal to 20 or 30 times its weight, boiled with it for ten minutes, solidifies on cooling to a pale mawkish jelly.
Microscopic Structure—The tissue of Chondus crispus is made up of globular or elongated, thick-walled cells. The superficial layers on both sides of the lobes constitute a kind of peel, easily separable in microscopic sections. The interior or medullary part exhibits a much less densely packed tissue formed of larger cells. The larger cavities of this tissue contain a granular mucilaginous matter, assuming a slight violet tinge on addition of iodine. In water however, the cell-walls swell up so as to form a gelatinous mass, in which separate cells can at last be scarcely distinguished.[2773] In the fresh state, its cells also contain granules of chlorophyll imbued with a red matter, termed Phyco-erythrin. But by washing and exposure to the air, these colouring substances are removed or greatly altered, and are no longer visible in the commercial drug.
Chemical Composition—The constituents of carrageen are those generally found in marine algæ, especially as regards the mucilage. This latter is insoluble in an ammoniacal solution of copper (Schweizer’s test); by the action of fuming nitric acid, it yields, in common with gum, an abundance of mucic acid. The mucilage of carrageen, like many similar bodies, obstinately retains inorganic matter; after it had three times been dissolved in water, and as many times precipitated with alcohol, we found it still to yield the same quantity of ash as the raw drug itself, that is to say, more than 15 per cent. The mucilage, perfectly dried, is a tough horny substance, of a greyish colour; it quickly swells up in water, forming a jelly which is precipitable by neutral acetate of lead.
By boiling carrageen for a week with water containing 5 per cent. of sulphuric acid, Bente (1876) obtained crystals of lævulinic acid, C₅H₈O₃, and an amorphous sugar. The former is also afforded by cellulose of pine wood and by paper.
According to Blondeau,[2774] the mucilage of carrageen contains 21 per cent. of nitrogen and 2·5 of sulphur, a statement which we are able to point out as erroneous. We find in it no sulphur, and only 0·88 per cent. of nitrogen. The drug itself yielded us not more than 1·012 per cent. of nitrogen.
When thin slices of the plant are treated with alcoholic potash, and then after washing left for 24 hours in contact with a solution of iodine in potassium iodide, they acquire a deep blue; yet, starch granules are not found in this seaweed. Lastly in connexion with carrageen may be mentioned Fucusol, an oily liquid isomeric with furfurol, obtained by boiling seaweeds with dilute sulphuric acid.
Commerce—The plant is collected on the west and north-west coast of Ireland: Sligo is said to be a great depôt for it. Carrageen of superior quality is sometimes imported from Hamburg.
The largest quantities of carrageen, sometimes half a million pounds a year, are gathered near Minot Ledge lighthouse, Scituate, Plymouth county, on the coast of Massachusetts, where a systematic process of preparing it for the market is adopted.[2775]
Uses—The mucilaginous decoction and jelly which carrageen affords are popular remedies in pulmonary and other complaints; but as nutriment such preparations are much over-estimated.[2776]
Carrageen is sometimes used for feeding cows and calves; and under the name of Alga marina, for stuffing mattresses. It is largely used for industrial purposes, like other mucilaginous matter. Its mucilage serves for thickening the colours employed in calico-printing, and as size for paper and for cotton goods. In America it is used for fining beer.
Substitutes—Gigartina mammillosa[2777] J. Agardh (Chondrus mammillosus Grev.) is collected indiscriminately with Ch. crispus. It is distinguished from the latter chiefly by having the flat portion of the thallus beset with elevated or stalked tubercles, bearing the cystocarps; but it has the same properties. G. acicularis Lamouroux, a species common on the coasts of France and Spain, and having slender cylindrical branches, is occasionally collected along with Chondrus crispus. Dalmon (1874) who has examined it, asserts it to be less soluble in boiling water than true carrageen. Small quantities of other seaweeds are often present through the negligence of the collectors.
FUCUS AMYLACEUS.
Alga Zeylanica; Ceylon Moss,[2778] Jaffna Moss.
Botanical Origin—Sphærococcus lichenoides Agardh. (Gracillaria lichenoides Grev., Plocaria candida Nees), a light purple or greenish seaweed, belonging to the class Florideæ, occurring on the coasts of Ceylon, Burma, and the Malay islands.[2779]
History—Ceylon moss has long been in use among the inhabitants of the Indian Archipelago and the Chinese. It is probably one of the plants described by Rumphius[2780] as Alga coralloides. In recent times it was brought to the notice of European physicians by O’Shaughnessy.[2781]
Description—The plant, which as found in commerce is opaque and white, having been deprived of colour by drying in the sun and air, consists of cylindrical ramifying stems or filaments, ⅒ of an inch in diameter and from 1 to 6 or more inches in length. The main stems bear numerous branches, simple or giving off slender secondary or tertiary ramifications, ending in a short point. When moistened, the plant increases a little in volume, becomes rather translucent, and frequently exhibits whitish globular or mammiform fruits (cystocarps). It is somewhat friable, and after drying at 100° C. may easily be powdered. It is devoid of taste and smell, in this respect differing from most sea weeds.
Microscopic Structure—The transverse section shows a loose tissue made up of large empty cells, enclosed by a cortical zone 30 to 70 mkm. thick. This zone consists of small cells, loaded with globular starch granules, from less than 1 up to 3 mkm. in diameter, so densely packed as to form what seems at first sight a single mass in each cell. In the larger cells the granules are attached to the walls; they do not display in polarized light the usual cross. The thick walls of the cells show a stratified structure, especially after having been moistened with chromic acid; on addition of a solution of iodine in an alkaline iodide, they assume a deep brown, but the starch granules, which also abound in the cystocarps, display the usual blue tint.
Chemical Composition—The drug, as examined by O’Shaughnessy, yielded in 100 parts of vegetable jelly 54·5, starch 15·0, ligneous fibre (cellulose?) 18·0, mucilage 4·0, inorganic salts 7·5.
Cold water removes the mucilage, which, after due concentration, may be precipitated by neutral acetate of lead. This mucilage, when boiled for some time with nitric acid, produces oxalic acid and microscopic crystals of mucic acid (beautifully seen by polarized light), soluble in boiling water and precipitating on cooling. With one part of the drug and 100 parts of boiling water a thick liquid is obtained which affords transparent precipitates with neutral acetate of lead or alcohol, in the same way as carrageen. With 50 parts of water, a transparent tasteless jelly, devoid of viscosity, is produced; in common with the mucilage, it furnishes mucic acid, if treated with nitric acid. Micro-chemical tests do not manifest albuminous matter in this plant.
Some chemists have regarded the jelly extracted by boiling water as identical with pectin, but the fact requires proof. Payen[2782] called it Gelose, and found it composed of carbon 42·77, hydrogen 5·77, and oxygen 51·45 per cent. Gum Arabic contains carbon 42·12, hydrogen 6·41, and oxygen 51·47 = C₁₂H₂₂O₁₁. Payen’s gelose imparts a gelatinous consistence to 500 parts of water; it is extracted by boiling water from the plant previously exhausted by cold water slightly acidulated.[2783]
The inorganic salts of Ceylon moss consist, according to O’Shaughnessy, of sulphates, phosphates, and chlorides of sodium and calcium, with neither iodide nor bromide. Dried at 100° C., it yielded us 9·15 per cent. of ash.
Uses—A decoction of Ceylon moss made palatable by sugar and aromatics, has been recommended as a demulcent, and a light article of food for invalids. In the Indian Archipelago and in China, immense quantities of this and of some other species of seaweed[2784] are used for making jelly and for other purposes.