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5. CYTISINE.

§ 466. The Cytisus Laburnum.—The laburnum tree, Cytisus laburnum, so common in shrubberies, is intensely poisonous. The flowers, bark, wood, seeds, and the root have all caused serious symptoms. The active principle is an alkaloid, to which the name of Cytisine has been given. The best source is the seeds. The seeds are powdered and extracted with alcohol containing hydrochloric acid, the alcohol distilled off, the residue treated with water and filtered through a wet filter to remove any fatty oil, the filtrate treated with lead acetate; and, after separating the precipitated colouring matter, made alkaline with caustic potash, and shaken with amyl alcohol. The amyl alcohol is shaken with dilute hydrochloric acid, the solution evaporated, the crude crystals of hydrochloride thus obtained treated with alcohol to remove colouring matters, and recrystallised several times from water; it then forms well-developed, colourless, transparent prisms. From the hydrochloride the free base is readily obtained.

Cytisine, C₁₁H₁₄N₂O.—To cytisine used to be ascribed the formula C₂₀H₂₇N₃O, but a study of the salt and new determinations appear to prove that it is identical with ulexine.[518] Cytisine is in the form of white radiating crystals, consisting, when deposited from absolute alcohol, of anhydrous prisms, which melt at from 152° to 153°. Cytisine has a strong alkaline reaction; it is soluble in water, alcohol, and chloroform, less so in benzene and amyl alcohol, almost insoluble in cold light petroleum, and insoluble in pure ether. The specific rotatory power in solution is [α]_D17° = -119·57.

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It is capable of sublimation in a current of hydrogen at 154·5°; the sublimate is in the form of very long needles and small leaflets; at higher temperatures it melts to a yellow oily fluid, again becoming crystalline on cooling. Cytisine is a strong base; it precipitates the earths and oxides of the heavy metals from solutions of the chlorides, and, even in the cold, expels ammonia from its combinations.

Cytisine forms numerous crystalline salts, among which may be mentioned two platinochlorides, C₁₁H₁₄N₂OH₂PtCl₆ + 2¹⁄₂H₂O and (C₁₁H₁₄N₂O)₂H₂PtCl₆, crystallising in golden yellow needles, which are tolerably soluble in water; and the aurochloride, C₁₁H₁₄N₂OHAuCl₄, crystallising in short, red-brown, hook-shaped needles; m.p. 212° to 213°, without evolution of gas.

§ 467. Reactions of Cytisine.—Concentrated sulphuric acid dissolves cytisine without colour; if to the solution is added a drop of nitric acid, it becomes orange-yellow, and on addition of a crystal of potassic bichromate, first yellow, then dirty brown, and lastly green. Concentrated nitric acid dissolves the base in the cold without colour, but, on warming, it becomes orange-yellow. Picric, tannic, and phosphomolybdic acids, potassic, mercuric, and potass. cadmium iodides, and iodine with potassic iodide, all give precipitates. Neither potassic bichromate nor mercuric chloride precipitates cytisine, even though the solution be concentrated. The best single test appears to be the reaction discovered by Magelhaes; this consists in adding thymol to a solution of cytisine in concentrated sulphuric acid, when a yellow colour, finally passing into an intense red, is produced.

§ 468. Effects on Animals.—W. Marmé found subcutaneous doses of from 30 to 40 mgrms. fatal to cats; death was from paralysis of the respiration, and could be avoided by artificial respiration. Cattle are sometimes accidentally poisoned by laburnum. An instance of this is recorded in the Veterinarian (vol. lv. p. 92). In Lanark a storm had blown a large laburnum tree down to the ground; it fell into a field in which some young heifers were grazing, and they began to feed on the leaves and pods. Two or three died, and three more were ill for some time, but ultimately recovered.

The laburnum, however, does not always have this effect, for there is a case related in the Gardeners’ Chronicle, in which five cows browsed for some time on the branches and pods of an old laburnum tree that had been thrown aside. Rabbits and hares are said to feed eagerly, and without injury, on the pods and branches.

§ 469. Effects on Man.—The sweet taste of many portions of the laburnum tree, as well as its attractive appearance, has been the cause of many accidents. F. A. Falck has been able to collect from medical literature no less than 155 cases—120 of which were those of the accidental poisoning of children: only 4 (or 2·6 per cent.), however, died, so that the poison is not of a very deadly character.

One of the earliest recorded cases is by Christison.[519] A servant-girl of Inverness, in order to excite vomiting in her fellow-servant (the cook), boiled some laburnum bark in soup; very soon after partaking of this soup, the cook experienced violent vomiting, which lasted for thirty-six hours; she had intense pain in the stomach, much diarrhœa, and great muscular weakness; she appears to have suffered from gastro-intestinal catarrh for some time, but ultimately recovered.

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Vallance[520] has described the symptoms observed in the poisoning of fifty-eight boys, who ate the root of an old laburnum tree, being allured by its sweet taste. All were taken ill with similar symptoms, differing only in severity; two who had eaten half an ounce (nearly 8 grms.) suffered with especial severity. The symptoms were first vomiting, then narcosis, with convulsive movements of the legs and strange movements of the arms: the pupils were dilated. This dilatation of the pupil Sedgwick also saw in the poisoning of two children who ate the root. On the other hand, when the flower, seeds, or other portions of the laburnum have been eaten, the symptoms are mainly referable to the gastro-intestinal tract, consisting of acute pain in the stomach, vomiting, and diarrhœa. On these grounds it is therefore more than probable that there is another active principle in the root, differing from that which is in those portions of the tree exposed to the influence of sunlight.[521]

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The post-mortem appearances are, so far as known, in no way characteristic.

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VII.—The Alkaloids of the Veratrums.

§ 470. The alkaloids of the veratrums have been investigated by Dr. Alder Wright, Dr. A. P. Luff, and several other chemists.[522]

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The method which Wright and Luff adopted to extract and separate these alkaloids from the root of V. album and V. viride, essentially consisted in exhausting with alcohol, to which a little tartaric acid has been added, filtering, distilling off the alcohol, dissolving the residue in water, alkalising with caustic soda, and shaking up with ether. The ethereal solution was next separated, and then washed with water containing tartaric acid, so as to obtain a solution of the bases as tartrates: in this way the same ether could be used over and over again. Ultimately a rough separation was made by means of the different solubilities in ether, pseudo-jervine being scarcely soluble in this medium, whilst jervine, veratralbine, veratrine, and cevadine are very soluble in it.

The yield of Wright and Luff’s alkaloids was as follows:—

TABLE SHOWING THE ALKALOIDS IN THE VERATRUMS.

	V. album. Per Kilo.			V. viride. Per Kilo.
Jervine,	1	·3	grm.		·2	grm.
Pseudo-jervine,		·4	„		·15	„
Rubi-jervine,		·25	„		·02	„
Veratralbine,	2	·2	„	Traces.
Veratrine,		·05	„	Less than ·004 grm.
Cevadine,	Absent.			Less„han	·43	4 „

From whence it appears that V. album has only a very small quantity of veratrine, that it is almost absent in V. viride; on the other hand, V. viride contains a fair quantity of cevadine, an alkaloid absent in V. album.

Besides the six principles enumerated, G. Salzberger has recently separated two other crystalline substances, to which he has given the names of protoveratrine and protoveratridine, and Pehkschen has also separated a ninth substance, to which he has given the name of veratroidine.

The formulæ of the nine bodies which have been separated from hellebore root are as follows:—

					Melting-point.
1.	Veratrine, C37H53NO11,				...
2.	Cevadine, C32H49NO9,				205°-206°
3.	Protoveratrine, C32H51NO11,				245°-250°
4.	Pseudo-jervine,	-		C29H43NO7 (Wright),	299°-300°
				C29H49NO12 (Pehkschen),	...
5.	Veratralbine, C28H43NO5,				...
6.	Protoveratridine, C26H45NO8,				265°
7.	Rubi-jervine,	-		C26H43NO2 (Wright and Luff),	236°
				C26H43NO2 (Salzberger),	240°-245°
8.	Jervine, C26H37NO32H2O,				237°-239°
9.	Veratroidine, C32H53NO9,				149°

Three of these alkaloids possess powerful sternutatory properties, the least quantity applied to the nostrils exciting sneezing; the three are veratrine, cevadine, and protoveratrine.

Protoveratrine, C₃₂H₅₁NO₁₁, has been obtained by G. Salzberger[523] from powdered hellebore root, by the following process:—

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The powdered root is first freed from fatty and resinous matters by treatment with ether, and then the fat-free powder is exhausted with alcohol. The alcohol is evaporated off in a vacuum, the extract mixed with much acetic acid water, filtered from the insoluble residue, and treated with metaphosphoric acid; the voluminous precipitate contains much amorphous matter, with insoluble compounds of jervine and rubi-jervine. The precipitate is filtered off, and the filtrate treated with excess of ammonia and shaken up with ether. On separating the ether and distilling, protoveratrine crystallises out, and can be obtained pure by recrystallisation from strong alcohol.

Protoveratrine crystallises in four-sided plates, which melt with charring at 245° to 250°. The base is insoluble in water, benzene, and light petroleum; chloroform and boiling 96 per cent. alcohol dissolve it somewhat; cold ether scarcely touches it, boiling ether dissolves it a little.

Concentrated sulphuric acid dissolves the alkaloid slowly with the production of a greenish colour, which passes to cornflower blue, and, after some hours, becomes violet. Sulphuric acid and sugar gives a different colour to that produced by commercial veratrine. There is first a green colour which darkens into olive green, then becomes dirty green, and finally dark brown. When warmed with strong sulphuric, hydrochloric, or phosphoric acids, there is a strong odour of isobutyric acid developed. Dilute solutions of the salts are precipitated by ammonia, Nessler’s reagent, gold chloride, potassium mercury iodide, cadmium iodide, phosphotungstic acid, and picric acid; no precipitate is produced by tannin, platinum chloride, or mercuric chloride.

§ 471. Veratrine (C₃₇H₅₃NO₁₁) is a crystallisable alkaloid, which is a powerful irritant of the sensory nerves of the mucous membrane, and excites violent sneezing. Treated with concentrated sulphuric acid, it dissolves with a yellow colour, deepening into orange, then into blood-red, and finally passing into carmine-red. If the freshly-prepared sulphuric acid solution is now treated with bromine water, a beautiful purple colour is produced. Concentrated hydrochloric acid dissolves veratrine without the production of colour, but, with careful warming, it becomes beautifully red. This reaction is very delicate, occurring with ·17 mgrm. On saponification veratrine yields veratric acid.

Veratric acid is procatechu-dimethylether acid, and has the constitutional formula,

Veratric acid

Veratric acid forms colourless needles and four-sided prisms which have a marked acid reaction; it melts on heating to a colourless fluid, and sublimes without decomposition; it is easily soluble in hot alcohol, but insoluble in ether. If dissolved in nitric acid, water separates nitro-veratric acid, C₉H₉(NO₂)O₄ which crystallises out of alcohol in small yellow scales. Veratric acid unites with bases forming crystalline salts; the silver salt has the composition of C₉H₉AgO₄ = 37·37 per cent. silver, and may assist in identification. It is crystalline with a melting point of 205° to 206°.

Cevadine, C₃₂H₄₉NO₉ (Merck’s veratrine).—It has powerful sternutatory properties, and, under the influence of alcoholic potash, yields tiglic[524] acid and cevine, C₂₇H₄₃NO₈.

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According to Ahrens, angelic acid is first formed, and then converted into tiglic acid. When the alkaloid is boiled with hydrochloric acid, tiglic acid is formed, and a ruby red mass. Nitric acid oxidises cevadine completely; with potassic permanganate it yields acetic and oxalic acids; with chromic acid it forms acetaldehyde and carbon dioxide.[525]

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The Continental authorities always give to cevadine the name of veratrine. Cevadine forms a crystalline aurochloride, a crystalline mercurochloride, C₃₂H₄₉NO₉HHgCl₃, and a crystalline picrate, C₃₂H₄₉NO₉C₆H₃N₈O₇. The mercury salt crystallises in small silvery plates, and melts with decomposition at 172°. The picrate forms stable crystals blackening at 225°; both of the latter salts are but little soluble in water, but are soluble in alcohol. Cevadine also unites with bromine, forming a tetrabromide, an amorphous yellow powder insoluble in water, but readily soluble in alcohol, ether, and chloroform.

§ 472. Jervine, (C₂₆H₃₇NO₃2H₂O) (Wright and Luff), C₁₄H₂₂NO₂ (Pehkschen),[526] crystallises in white needles, and, when anhydrous, melts at 237·7°. It is slightly lævorotatory. At 25° one part of the base dissolves in 1658 benzene, 268 ether, 60 chloroform, and 16·8 absolute alcohol. It is insoluble in light petroleum, and but slightly soluble in ethyl acetate, water, or carbon bisulphide. It forms a very insoluble sulphate, and a sparingly soluble nitrate and hydrochloride. Jervine gives, with sulphuric acid and sugar, a violet colour, passing to blue. Treated with strong sulphuric acid it dissolves to a yellow fluid, which becomes successively dark yellow, brownish yellow, and then greenish. The green shade is immediately developed by diluting with water. Jervine does not produce sneezing.

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§ 473. Pseudo-jervine, C₂₉H₄₃NO₇ (Wright), m.p. 299°; C₂₉H₄₉NO₁₂, m.p. 259° (Pehkschen), may be obtained in a crystalline state. One part is soluble in 10·9 parts of light petroleum, 372 parts of benzene, 1021 parts of ether, 4 of chloroform, and 185 of absolute alcohol. The pure base gives no colour with sulphuric, nitric, or hydrochloric acids. It does not produce sneezing.

§ 474. Protoveratridine, C₂₆H₄₅NO₈, is probably derived from protoveratrine. Salzberger[527] isolated it from powdered hellebore roots by treating the powder with barium hydroxide and water, and extracting with ether. The ether extract was separated and freed from ether in a current of hydrogen at a low temperature.

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From the dark green syrup obtained jervine crystallised out, and from the mother liquor ultimately protoveratridine was separated.

Protoveratridine crystallises in colourless four-sided plates, which melt at 265°. It is almost insoluble in alcohol, chloroform, methyl alcohol, and acetone, and insoluble in benzene, light petroleum, and ether. Concentrated sulphuric acid gives a violet, then a cherry-red colour. Its solution in concentrated hydrochloric acid becomes light red on warming, and there is an odour of isobutyric acid. It is readily soluble in dilute mineral acids, and the solution, on the addition of ammonia, yields the alkaloid in a crystalline condition. The sulphuric acid solution gives precipitates with phosphotungstic, picric, and tannic acids, and with potassium mercury iodide; but gives no precipitate with platinum chloride, potassium-cadmium iodide, or with Millon’s reagent.

It forms a platinum salt, (C₂₆H₄₅NO₈)₂H₂PtCl₆ + 6H₂O, which is precipitated in large six-sided plates on adding alcohol to a mixed solution of platinum chloride and a salt of the base.

Protoveratridine is not poisonous, and does not cause sneezing. Its solutions are very bitter.

§ 475. Rubi-jervine, C₂₆H₄₃NO₂, is a crystallisable base wholly different from jervine, yet probably closely allied to it. It forms a light yellow, indistinctly crystalline gold salt (C₂₆H₄₃NO₂,HCl,AuCl₃): it gives a different play of colours from jervine with sulphuric acid. The concentrated acid dissolves rubi-jervine to a clear yellow fluid, becoming successively dark yellow, brownish yellow, and brownish blood-red, changing after several hours to a brownish purple. On diluting slightly with water the brownish-red liquid, it becomes successively crimson, purple, dark lavender, dark violet, and ultimately light indigo. Its hydrochloride and sulphate are both more soluble than either of the corresponding salts of jervine or pseudo-jervine.

§ 476. Veratralbine, C₂₈H₄₃NO₅, an amorphous non-sternutatory base, gives, when a speck of the substance is dissolved in sulphuric acid, a play of colours, becoming successively yellow, dark yellow, brownish orange, and brownish blood-red, with a strong green fluorescence. It yields no acid on saponification.

§ 477. Veratroidine, C₃₂H₅₃NO₉, is another base which has been separated by C. Pehkschen.[528] Its melting point is 149°. One part dissolves in 13 of benzene, 59 of chloroform, and 9 of ether. It yields amorphous salts with the mineral acids, and with oxalic and acetic acids. It is precipitated by most of the group reagents. With 11 per cent. solution of hydrochloric acid it gives a beautiful rose colour.

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§ 478. Commercial Veratrine.—Commercial veratrine is a mixture of alkaloids, and has usually fairly constant properties, one of which is its intense irritant action on the nostrils. Placed on moist blue-red litmus paper it gives a blue spot. It is but little soluble in water, 1 : 1500; but readily dissolves in alcohol and chloroform; it is but little soluble in amyl alcohol, benzene, and carbon disulphide.

When a very small quantity is treated with a drop of sulphuric acid, the acid in the cold strikes a yellow colour; on warming, the colour becomes violet, slowly changing to orange and cherry red. Sensible to 100th of mgrm. If this test is performed in a test-tube, a green-yellow fluorescence is also seen on the sides of the test-tube.

Commercial veratrine strikes a pink-red colour with hydrochloric acid in the cold if a long time is allowed to elapse, but it at once appears if the acid is warmed, and is permanent. The solution becomes fluorescent if two drops of acetic acid are added.

If a small quantity of commercial veratrine is added to melted oxalic acid and the warming continued, a blood-red colour is obtained.

Veratrine, warmed with syrupy phosphoric acid, develops an odour of butyric acid.

A dark green colour, followed by reddish purple and blue colours, is obtained by adding a sprinkling of finely-powdered sugar to a solution of veratrine in sulphuric acid. This is best seen with a solution of 1 to 10,000; if in dilution of 1 to 100,000 a grass-green colour is produced, followed by purple and blue colours, quickly changing to brown or black.[529]

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When two or three drops of sulphuric acid and furfur aldehyde (5 drops to 10 c.c. of acid) are added to minute particles of alkaloids, a more or less characteristic colour makes its appearance; this is particularly the case with veratrine. A few particles rubbed with a glass rod, and moistened with the reagent, gives first a yellowish-green, then an olive-green mixture, the edges afterwards becoming a beautiful blue. On warming, the mixture gradually acquires a purple-violet colour. The blue substance obtained in the cold is insoluble in alcohol, ether, or chloroform. The least amount of water decolorises the solution, and, on adding much water, a fairly permanent yellow solution is obtained.[530]

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§ 479. Pharmaceutical Preparations.—The alkaloid is officinal in the English, American, and Continental pharmacopœias. There is also an unguentum veratrinæ—strength about 1·8 per cent. In the London pharmacopœia of 1851 there used to be a wine of white hellebore, the active principle of 20 parts of the root by weight being contained in 100 parts by measure of the wine. Such a wine would contain about 0·084 per cent. of total alkaloids. Of the green hellebore there is a tincture (tinctura veratri viridis), to make which four parts by weight of the root are exhausted by 20 parts by measure of spirits; the strength varies, but the average is 0·02 per cent. of total alkaloids.

§ 480. Fatal Dose.—The maximum dose of the commercial alkaloid is laid down as 10 mgrms. (·15 grain), which can be taken safely in a single dose, but nothing sufficiently definite is known as to what is a lethal dose. 1·3 grm. of the powdered rhizome has caused death, and, on the other hand, ten times that quantity has been taken with impunity, so that at present it is quite an open question.

§ 481. Effects on Animals—Physiological Action.—Experiments on animals have proved that the veratrums act on the sensory nerves of the skin, and those of the mucous membranes of the nose and intestinal canal; they are first excited, afterwards paralysed. When administered to frogs, sugar and lactic acid appear in the urinary excretion.[531] It exercises a peculiar influence on voluntary muscle; the contractility is changed, so that, when excited, there is a long-continuing contraction, and from a single stimulus more heat is disengaged than with healthy muscle; the motor nerves are also affected. The respiration, at first quickened, is then slowed, and finally paralysed. The heart’s action is also first quickened, the blood-pressure at the same time is raised, and the small arteries narrowed in calibre; later follow sinking of the pressure, slowing of the heart, and dilatation of the vessels, and the heart becomes finally paralysed.

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§ 482. Effects on Man.—Poisoning by veratrum, sabadilla, or pharmaceutical preparations containing veratrine, is not common. Plenk witnessed a case in which the external application of sabadilla powder to the head caused delirium, and Lentin also relates a case in which an infant at the breast seems to have died from an external application made for the purpose of destroying lice. In both instances, however, there is a possibility that some of the medicament was swallowed.

Blas recorded, in 1861, the case of two children who drank a decoction of white hellebore, the liquid being intended as an external application to an animal. They showed serious symptoms, but ultimately recovered.

A scientific chemist took 3·8 grms. (58 grains) of the tincture of green hellebore for the purpose of experiment. There followed violent symptoms of gastric irritation, vomiting, and diarrhœa, but he also recovered.[532]

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Casper relates the poisoning of a whole family by veratrum; from the stomach of the mother (who died) and the remains of the repast (a porridge of lentils) veratrine was separated.

Faber[533] recorded the poisoning of thirty cows by veratrum; eight died, and it is noteworthy that violent poisonous symptoms were produced in animals partaking of their flesh and milk.

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§ 483. The symptoms appear soon after the ingestion, and consist of a feeling of burning in the mouth, spreading downwards to the stomach, increased secretion of saliva, and difficulty of swallowing; then follow violent vomiting and diarrhœa, with great pain in the bowels, often tenesmus; there is also headache, giddiness, a feeling of anxiety, and the pupils are dilated. The consciousness is ordinarily intact; the pulse is weak and slow, and the breathing embarrassed; the skin is benumbed. There may be also formicating feelings, and twitchings in the muscles with occasionally the tetanic cramps, which are constantly seen in frogs. In cases which end fatally, the disturbance of the breathing and circulation increases, and death takes place in collapse.

An important case of slow poisoning is on record,[534] in which two brothers, aged twenty-one and twenty-two years, died after nine and eleven weeks of illness, evidently from repeated small doses of the powder of Veratrum album. They became very weak and thin, suffered from diarrhœa and bloody stools, sleeplessness, disturbance of the intellect, and delirium.

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§ 484. The post-mortem signs do not appear distinctive; even in the case just mentioned—in which one would expect to find, at all events, an extensive catarrh of the intestinal canal—the results seem to have been negative.

§ 485. Separation from Organic Matters.—The method of Stas (by which the organic matters, whether the contents of the stomach or the tissues, are treated with alcohol, weakly acidified by tartaric acid) is to be recommended. After filtering, the alcoholic extract may be freed from alcohol by careful distillation, and the extract taken up with water. By now acidifying gently the watery extract, and shaking it up with ether and chloroform, fatty matters, resinous substances, and other impurities, are removed, and it may then be alkalised by soda or potash, and the veratrine extracted by ether. The residue should be identified by the hydrochloric acid and by the sulphuric acid and bromine reactions; care should also be taken to ascertain whether it excites sneezing.

A ptomaine, discovered by Brouardel,[535] was described by him as both chemically and physiologically analogous to veratrine. A. M. Deleziniere[536] has since investigated this substance. Only when in contact with air does the analogy to veratrine obtain, and Deleziniere, to ascertain its reactions, studied it when in an atmosphere of nitrogen. It appears to be a secondary monamine, C₃₂H₃₁N, and is in the form of a colourless, oily liquid, with an odour like that of the hawthorn. It is insoluble in water, but alcohol, ether, toluene, and benzene dissolve it readily. It oxidises in the presence of air. The salts are deliquescent.

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VIII.—Physostigmine.

§ 486. The ordeal bean of Calabar (Physostigma faba) is a large, all but tasteless, kidney-shaped bean, about an inch in length, and half an inch thick; its convex edge has a furrow with elevated ridges, and is pierced by a small hole at one extremity. The integuments are coffee-brown in colour, thin, hard, and brittle; they enclose two white cotyledons, easily pulverisable, and weighing on an average 3·98 grms. (61 grains). The seed contains at least one alkaloid, termed Physostigmine (first separated in 1864 by Jobst and Hesse), and possibly a second, according to Harnack and Witkowsky, who have discovered in association with physostigmine a new alkaloid, which they call Calabarine, and which differs from physostigmine in being insoluble in ether and soluble in water. It is also soluble in alcohol; and further, the precipitate produced by potassium iodo-hydrargyrate in calabarine solutions is insoluble in alcohol.

§ 487. Physostigmine, or eserine, is not easily obtained in a crystalline state, being most frequently extracted as a colourless varnish, drying into brittle masses. It is, however, quite possible to obtain it in the form of partially-crystalline crusts, or even rhombic plates, by care being taken to perform the evaporation, and all the operations, at as low a temperature as possible, and preferably in a dimly-lit room; for, if the temperature rises to 40°, much of the alkaloid will be decomposed. Hesse recommends that the beans be extracted, alcohol by the alcoholic solution alkalised by sodic carbonate, and the liquid shaken up with ether, which will retain the alkaloid. The ether solution is now separated, and acidified slightly with very dilute sulphuric acid; the fluid, of course, separates into two layers, the lower of which contains the alkaloid as a sulphate, the upper is the ether, which is withdrawn, and the acid fluid passed through a moist filter. The whole process is then repeated as a purification.

Again, Vee, who has repeatedly obtained the alkaloid in a crystalline condition, directs the extraction of the beans by alcohol, the alcoholic solution to be treated as before with sodic carbonate, and then with ether; the ethereal solution to be evaporated to dryness, dissolved in dilute acid, precipitated by sugar of lead, and the filtrate from this precipitate alkalised by potassic bicarbonate, and then shaken up with ether. The ethereal solution is permitted to evaporate spontaneously, the crystalline crusts are dissolved in a little dilute acid, and the solution is lastly alkalised by potassic bicarbonate, when, after a few minutes, crystalline plates are formed.

The formula ascribed to physostigmine is C₁₅H₂₁N₃O₂. It is strongly alkaline, fully neutralising acids and forming tasteless salts. It is easily melted, and perhaps partly decomposed, at a temperature of 45°; at 100° it is certainly changed, becoming of a red colour, and forming with acids a red solution. It dissolves easily in alcohol, ether, chloroform, and bisulphide of carbon, but is not easily soluble in water.

The salts formed by the alkaloid with the acids are generally hygroscopic and uncrystallisable, but an exception is met with in the hydrobromide, which crystallises in stellate groups.[537] If CO₂ is passed into water containing the alkaloid in suspension, a clear solution is obtained; but the slightest warmth decomposes the soluble salt and reprecipitates the alkaloid. The hydrarg-hydroiodide (C₁₅H₂₁N₃O₂,HI,2HgI) is a white precipitate, insoluble in water, becoming yellow on drying, soluble in ether and alcohol, and from such solutions obtained in crystalline prismatic groups. A heat of 70° melts the crystals, and they solidify again in the amorphous condition.

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