Part 183

The therapeutic action of gelsemium is believed to be due to the sedative effect it exercises on the nervous and arterial systems--hence its power in controlling the nervous irritability so prevalent during fever. In moderate doses it causes a sensation of agreeable langour, accompanied with muscular relaxation; in larger doses, dizziness, dilated pupil, double vision, general muscular debility and prostration; these symptoms being accompanied by a diminution in the force and frequency of the pulse as well as in the respiration. At the same time the patient becomes insensible to pain; but is free from stupor and delirium. These symptoms are said to pass off, after a time, and to be attended with no unpleasant results.

The 'Lancet' as well as many of the American medical journals record several cases of poisoning arising from giving an overdose of this drug. The symptoms are a great prostration of nervous energy, accompanied by paralysis of sensation and motion. When death occurs it is probably owing to syncope. The antidotes are, first, an emetic, and after this has acted, stimulants, such as carbonate of ammonia with brandy, or aromatic spirits of ammonia. In cases accompanied with insensibility, recourse should be had to electricity.

Kollock, in the 'American Journal of Pharmacy' for 1855, states that he found the root on analysis to yield volatile oil, dry acrid resin, fatty resin, fixed oil, gallic acid, starch, pectic acid, albumen, extractive matter, lignin, gum, a yellow colouring matter, mineral matter (chiefly salts of potassium, calcium, magnesium, iron and silica), and an alkaloid, to which the name gelseminine or gelsemia has been given. Kollock also states that the leaves and flowers contain the same ingredients as the root, although in much smaller quantities.

Eberle, in the 'American Journal of Pharmacy' for 1864, says he failed to obtain gelseminine from the root. In a paper contributed to the 'American Journal of Pharmacy,' for January, 1870, by Dr Wormley, the author stated that he said he not only succeeded in obtaining pure gelseminine from the root, but also a peculiar acid which he calls gelseminic, or gelsemic[331] acid; which he regards as existing in combination with the gelsemia, forming the gelsemate of gelsemia.

[Footnote 331: Professor Sonneschien, having submitted the so-called _Gelseminic Acid_ to analysis thinks there can be no doubt that it is perfectly identical with æsculin, a glucoside obtained from the bark of the horse-chesnut--the _Esculus hippocastanum_.]

Probably the alkaloid gelseminine may at some future time be introduced into medicine, since it would appear to be the chief ingredient to which the root owes its activity. It is strongly poisonous. Dr Wormley injected one eighth of a grain under the skin of a large cat, which in 40 minutes exhibited great prostration, and died in an hour and a half from the time of the injection of the poison. The properties of the gelseminic acid, the resin, the volatile oil, and other ingredients of the root, have not been fully investigated. See TINCTURE OF GELSEMIUM, GELSEMININE.

In the 'American Journal of Pharmacy' for April, 1877, Dr Wormley gives the following directions for the preparations of gelseminic acid, and gelsemine:--A given volume of fluid extract, acidulated with acetic acid, is slowly added with constant stirring to about eight volumes of water; after the separated resinous matter has completely deposited, the liquid is filtered, and the filtrate concentrated on a water bath, to something less than the volume of fluid extract employed. The gelseminic acid is then extracted from the concentrated fluid by ether, after which the liquid is treated with slight excess of carbonate of sodium, and the gelsemine extracted with ether or chloroform. For the extraction of the first of these principles, it is not essential that the liquid should be acidulated, but in the presence of a free acid the results are more satisfactory.

=GEMS=. _Syn_. JEWELS; GEMMÆ, L. "Gems are precious stones, which, by their colour, limpidity, lustre, brilliant polish, purity, and rarity, are sought after as objects of dress and decoration. They form the principal part of the crown jewels of kings, not only from their beauty, but because they are supposed to comprise the greatest value in the smallest bulk; for a diamond, no larger than a nut, or an acorn, may be the representative sign of the territorial value of a whole country, the equivalent in commercial exchange for a hundred fortunes, acquired by severe toils and privations." "Among these beautiful minerals mankind have agreed in forming a select class, to which the title of gems or jewels has been appropriated; while the term precious stone is more particularly given to substances which often occur under a more considerable volume than fine stones ever do. Diamonds, sapphires, emeralds, rubies, topazes, hyacinths, and chrysoberyls, are reckoned the most valuable gems;--crystalline quartz, pellucid, opalescent, or of various hues, amethyst, lapis lazuli, malachite, jasper, agate, &c., are ranked in the much more numerous and inferior class of ornamental stones." (Ure.)

_Tests._ The only tests applicable to gems and precious stones are the determination of their relative hardness and their specific gravity. By the first test, pastes or factitious gems are readily detected; but beyond this, owing to the difficulty of applying it, it ceases to be useful to persons unconnected with the trade. The determination of the specific gravity is, however, of more general application, as gems are generally dismounted when offered for sale, or are so set that they may be removed from their 'mountings' without injury or inconvenience. See SPECIFIC GRAVITY, and _below_.

_Obs._ The relative hardness of the different substances is measured by the power they possess of cutting or scratching the other substances having a smaller number attached to them in the table. Thus, no gem but the DIAMOND (20) will scratch either the RUBY (17) or the SAPPHIRE (16); and, for the same reason, a blue stone that will cut the EMERALD or the TOPAZ can be no other than the SAPPHIRE. The sp. gr. is ascertained in the usual manner, and will be found sufficiently indicative of the true nature of the stone when considered in connection with its other characteristics. The index of refraction is a certain key to the quality of the stone, in the hands of those who are capable of determining it, and may be applied to either mounted or unmounted gems. The most convenient instrument for the purpose is Wollaston's 'REFLECTING-GONIOMETER,'

=Gems, Facti''tious.= These, with few exceptions, are made of very pure, fusible, highly transparent, and dense glass, usually termed 'PASTE' or 'STRASS,' which is generally formed of oxide of lead, potassa, and silica, with small quantities of other ingredients to increase the brilliancy and clearness. The characteristic tints are imparted by the addition of metallic oxides. The beauty of artificial stones and gems depends, chiefly, upon the tint of the real stones being exactly imitated, and upon proper care and skill being exercised in the cutting, polishing, and mounting them. All the coloured glasses, and enamels, may be worked up into artificial gems.

TABLE _of the Hardness, Specific Gravity, and Refractive Power of the principal_ GEMS _and_ PRECIOUS STONES, _and some other_ MINERALS; _compiled expressly for this work_.

| Name. | Relative | Specific Gravity. | Index of Reflection. | | | Hardness. | | | ---------------------------------------------------------------------------------| | Agate | 12 | 2·6 | | | Amethyst (occidental) | 11 | 2·7 | | | Calcareous spar | 6 | 2·7 | | | Chalk | 3 | 2·7 | | | Chrysolite | 10 | 3·7 | | | Cornelian | 11 | 2·7 | | | Crystal | 11 | 2·6 | | | Diamond (bluish) | 19 | 3·3 | } | | " (cubic) | 18 | 3·2 | } | | " (from Ormus) | 20 | 3·7 | } 2·439 | | " (pink) | 19 | 3·4 | } | | " (yellowish) | 19 | 3·3 | } | | " (average colourless)| 19 to 20 | 3·3 to 3·55 | } | | Emerald | 12 | 2·8 | | | Fluor spar | 7 | 3·5 | 1·434 | | Garnet | 12 | 4·4 | 1·815 | | Glass | { } | 2·3 to 3·62 | 1·525 to 2·028 | | " (crystal or flint) | {various} | 3·0 " 3·6 | 1·830 " 2·028 | | " (plate) | { } | 2·5 " 2·6 | 1·514 " 1·542 | | Gypsum | 5 | 2·3 | | | Jasper (green) | 11 | 2·7 | | | " (reddish yellow) | 9 | 2·6 | | | Onyx | 12 | 2·6 | | | Opal | 10 | 2·6 | | | Quartz | 10 | 2·7 | 1·548 | | Ruby | 17 | 4·2 | } 1·779 | | " (pale, from Brazil) | 17 | 3·5 | } | | " (spinelle) | 13 | 3·4 | 1·764 | | Sapphire (deep blue) | 16 | 3·8 | } 1·794 | | " (paler) | 17 | 3·8 | } | | Sardonyx | 12 | 2·6 | | | Schoerl | 10 | 3·6 | | | Topaz | 15 | 4·2 | | | " (Bohemian) | 11 | 2·8 | | | " (whitish) | 14 | 3·5 | | | Tourmaline | 10 | 3·0 | | | Zeolite | 8 | 2·1 | | | Zircon | -- | -- | 1·961 | ----------------------------------------------------------------------------------

MM. Fremy and Feil have lately succeeded in manufacturing artificial corundum, ruby and topaz, having a composition the same as the natural stones. The process by which they have effected this consists in fusing together at a red heat, in the furnace of a glass works for a considerable time, a fusible aluminate (such as aluminate of lead), and some silicious body.

The silica is found to unite with the lead, and to liberate the alumina in the crystalline form. When equal weights of alumina and red lead are heated together in a crucible made of some refractory silicious substance, the above conditions if the temperature has been maintained sufficiently long and high ensue, and there is found in the crucible at the end of the operation a layer of silicate of lead, and very frequently another of pure crystallised alumina or corundum.

The ruby colour is given by adding to the mixture in the crucible two or three per-cent. of bichromate of potash, the blue being produced by the addition of a small quantity of oxide of cobalt, with a trace only of bichromate of potash. A film of silicate of lead very frequently adheres to the ruby crystals, and this has to be removed.

In some instances, however, the crystals occur nearly pure, and are precisely similar to the natural gems in crystalline form, composition, hardness, and lustre.

Upon being heated, the artificial ruby, like the natural one, loses its rose colour, and recovers it again on cooling. It is said that the factitious gems hitherto obtained are not, as a rule, equal in lustre to the natural ones, and are consequently not so well suited for jewellers' work; also that they do not present to the lapidary conditions favorable to cleavage or cutting. They are, however, very well adapted for the works of watches. See ENAMELS, PASTES, &c.

=GENE'VA.= See GIN and HOLLANDS.

=GEN'TIAN ROOT.= _Syn._ GENTINÆ RADIX, L. The dried root of _Gentiana lutea_, or 'yellow gentian.' _Dose_, 10 to 30 gr.; as a simple bitter tonic, and stomachic, in dyspepsia, loss of appetite, gout, &c. It was formerly a favourite remedy in agues. "Joined with galls or tormentil, and given in sufficient quantity, it has not failed in any intermittents in which I have tried it." (Dr Cullen.) In excessive doses it is apt to relax the bowels and disturb the system. When taken for some time, it imparts its bitter flavour to the perspiration and urine. See DECOCTION, EXTRACT, &c.

=GEN'TIANIN.= _Syn._ GENTIANINE; GENTIANINA, L. A substance obtained by MM. Henry and Caventou from the root of common gentian.

_Prep._ 1. Gentian root (in powder) is digested for 2 or 3 days in cold ether, with agitation, and the filtered tincture evaporated to dryness; the residuum is dissolved in rectified spirit, and the solution is again evaporated; the semi-crystalline mass is, lastly, redissolved in either alcohol or ether, and crystallised by careful evaporation.

2. (Magendie.) The ethereal extract is exhausted with cold alcohol (rectified spirit), as before, and the resulting tincture is evaporated to dryness; the residuum is dissolved in water, calcined magnesia added in excess, and the whole boiled and filtered; the sediment is digested in ether, and the ethereal tincture allowed to crystallise by slow evaporation.

_Prop., &c._ Gentianin forms golden-yellow needles, scarcely soluble in cold water, but very soluble in alcohol and ether. It is a powerful bitter and stomachic.--_Dose_, 1/2 gr. to 2 gr.

=GER'MAN PASTE.= _Prep._ From pea-meal, 2 lbs.; sweet almonds (blanched), 1 lb.; fresh butter or lard, 1/4 lb.; moist sugar, 5 oz.; hay saffron, 1/2 dr.; beat to a smooth paste, adding cold water q. s., granulate the mass by passing it through a colander, and expose the product to the air in a warm place, until quite hard and dry. The addition of 2 or 3 eggs improves it. Used to feed larks, nightingales, and other insectivorous birds. It will keep good for 12 months in a dry place.

=GER'MAN SILVER.= _Syn._ ALBATA, ARGENTAN, _Electrum_, NICKEL SILVER, TUTENAG, VIRGINIAN PLATE, WHITE COPPER. A well-known alloy, the finer varieties of which nearly equal silver in whiteness and susceptibility of receiving a high polish, whilst they surpass it in hardness and durability. The following formulæ are from the highest authorities, or are the results of actual analysis of the finest commercial samples:--

_Prep._ 1. Copper, 50 parts; nickel, 20 parts; zinc, 30 parts. Very malleable, and takes a high polish.

2. Copper, 50 parts; nickel, 26 parts; zinc, 24 parts. Closely resembles silver; an excellent sample.

3. Copper and zinc, of each 41 parts; nickel, 18 parts. Rather brittle.

4. (M. Gersdorff.) Copper, 50 parts; nickel and zinc, of each 25 parts. Very white and malleable, and takes a high polish. Recommended as a general substitute for silver.

5. (Gersdorff.) Copper, 60 parts; nickel and zinc, of each 20 parts. For castings, as bells, candlesticks, &c.

6. (Gersdorff.) Copper, 60 parts; nickel, 25 parts; zinc, 20 parts. For rolling and wire. Very tough and malleable.

7. (Sample made from the ore of Hilburghausen.) Copper, 40-1/2 parts; nickel, 31-1/2 parts; iron, 2-1/2 parts; zinc, 25-1/2 parts. Equal to the best Chinese sample.

8. (Pelouze.) Copper and nickel, equal parts. Recommended by M. Pelouze as superior to any of the alloys containing zinc.

9. (Pelouze.) Copper, 2 parts; nickel, 1 part. Not so white as the last, but more malleable.

10. (White Copper from China.)--_a._ Copper, 30 parts; nickel, 36 parts; zinc, 34 parts.

_b._ (Said to be prepared from native ore.) Copper, 41 parts; nickel, 32 parts; iron, 2-1/2 parts; zinc, 24-1/2 parts. Silvery white, takes a high polish, very sonorous, malleable both cold and at a dull-red heat, and may be rolled into leaves or formed into wire.

11. (White metal spoon, sold as 'German Plate.') Copper, 55 parts; nickel, 24 parts; zinc, 16 parts; tin, 3 parts; iron, 2 parts.

_Anal._ This may be briefly described as follows:--_a._ 100 gr. of the alloy is digested in nitric acid q. s., diluted with a little water. If the sample is unequally attacked by the acid, and a white external shell is observed which dissolves more slowly than the internal portion, it is 'plated' on those parts with silver. If this silver shell or casing has a polished surface on both sides, the article has been 'electro-plated,' if the contrary is the case, it has most probably been plated in the usual way.

_b._ The solution being completed, heat is applied to expel the excess of acid, and the remainder is largely diluted with distilled water; dilute hydrochloric acid is now dropped in as long as it occasions a precipitate, and the whole, after being moderately heated for a short time, and cooled, is thrown upon a small paper filter; the precipitate on the filter is next washed with distilled water, carefully dried, and ignited in a small porcelain crucible, the filter itself being separately burnt on the cover of the crucible, and the ashes added to its contents prior to ignition. Every 143-1/2 gr. of the resulting fused chloride is equal to 108 gr. of metallic silver.

_c._ The filtered liquid (see _b_) is next treated with a stream of sulphuretted hydrogen, and the black precipitate is collected, washed, and digested in strong nitric acid; when the solution is complete sulphuric acid is dropped in to precipitate the lead (if any is present); if a precipitate is formed, the whole is evaporated to dryness, and the excess of sulphuric acid expelled by a rather strong heat applied towards the end; the dry mass is now collected on a filter, washed with a mixture of water and alcohol, dried, and exposed to slight ignition in a porcelain crucible. Every 152 gr. of the resulting dry sulphate is equal to 104 gr. of lead.

_d._ The liquor filtered from the sulphate of lead, or (in its absence) the nitric solution of the precipitate produced by the sulphuretted hydrogen (see _c_), is next treated with potassa, &c., as described under the analysis of brass. Every 40 gr. of the dry protoxide thus obtained represents 32 gr. of pure copper.

_e._ The liquor which was filtered from the precipitate produced by the sulphuretted hydrogen (see _c_) is boiled until it loses its offensive odour, and is then precipitated with carbonate of soda, in slight excess, and again boiled for a few minutes; the precipitate (mixed oxides of nickel and zinc) is collected, washed, and redissolved in dilute acetic or nitric acid, in excess; a current of sulphuretted hydrogen is next passed through the solution, the precipitate collected on a filter, washed, redissolved in hydrochloric acid, and the solution again treated with carbonate of soda; the last precipitate (oxide of zinc) is washed, dried, and gently ignited. Every 40 gr. of this oxide is equivalent to 32 gr. of metallic zinc.

_f._ The washings of the precipitated oxides and the liquid filtered from the precipitate occasioned by the sulphuretted hydrogen (see _e_) are mixed together, pure solution of ammonia added in considerable excess, and the mixture agitated for some time; the undissolved portion of the precipitate is then collected on a filter, washed with distilled water, redissolved in dilute nitric acid, again precipitated with solution of potassa, and this last precipitate (ferric oxide) washed, dried, ignited, and weighed. Every 80 gr. represents 50 gr. of metallic iron.

_g._ The ammoniacal solution filtered from the precipitate of sesquioxide of iron (see _f_) is precipitated with pure solution of potassa, boiled for a few minutes, and, when cold, thrown on a filter; the precipitate is, lastly, washed with hot water, dried, ignited, and weighed. Every 37-1/2 gr. of the oxide thus obtained is equal to 29-1/2 gr. of metallic nickel.

_Obs._ The manufacture of nickel or German silver has of late acquired an importance which is second only to that of silver plate itself. The superior quality of this alloy, and the graceful patterns which it is often made to assume in the hands of the accomplished artist cannot fail to have attracted the admiration of the majority of our readers. The value of correct information regarding the preparation of this alloy, and of a ready method of determining the composition of the most improved commercial samples will, therefore, be fully appreciated by every metallurgist who wishes to throw his wares into the arena of public competition. Much that is vended under the name of GERMAN SILVER is little better than the BRITANNIA METAL or PLATE PEWTER formerly so plentiful in every establishment in this country. German silver has quite superseded copper as the basis of 'electro-plated goods.'[332]

[Footnote 332: See ELECTROTYPE.]

The union of the metals in the above formulæ is effected by heat with the usual precautions. When iron is ordered, it is generally added under the form of 'tin plate.' See ALLOY, BRASS, BRITANNIA METAL, BRONZE, &c.

=GER'MAN TIN'DER.= See AMADOU.

=GERMINA'TION.= The growth or vegetation of a seed by which a young plant is produced. The conditions essential to germination are the presence of warmth, air, and moisture. The most favorable temperature is between 60° and 85° Fahr., according to the habitat of the respective plants. Below 40° Fahr. most of the more perfect seeds either refuse to vegetate, or vegetate slowly and feebly; and at or near the freezing-point none of them undergo this change. At a temperature above 100° Fahr. the young germ is usually injured, and at about 125°, if it forms, it soon withers and dies. See MALTING, SEED, &c.

=GERMS.= The 'germ theory of disease' may be briefly stated to be that which supposes the cause of epidemic and contagious maladies to be due to the agency of specific, inconceivably small germs,--different germs giving rise to different diseases.

These disease germs gaining an entrance by means of air, water, or food into the healthy body, and being possessed of extraordinary powers of increase and subdivision, are supposed to set up the particular disease, and at the same time to multiply to an incredible extent by feeding upon the tissues best suited for their support. Further, they are conceived to be thrown off into the atmosphere from the body of the patient, whence they are conveyed as before described into other healthy animal organism, in which, comporting themselves as in the previous case, they set up a similar disease. See BACTERIA AS ORIGINATORS OF DISEASE.