Part 2 — CHAPTER XIV. OF POISONING WITH MERCURY.
Reading edition
The next genus of the metallic poisons includes the preparations of mercury. Some of these are hardly less important than the arsenical compounds. They act with equal energy, produce the same violent symptoms, and cause death with the same rapidity. They have therefore been often given with a criminal intent; and have thus become the subject of inquiry upon trials. In another respect, too, they claim the regard of the medical jurist: their effects on the body, when insidiously introduced in the practice of the arts in which mercury is used, form a branch of that department of medical police, which treats of the influence of trades on the health.
Section I.—Of the Chemical History and Tests for the preparations of Mercury.
Mercury is a fluid metal, exceedingly brilliant, of a silver-white colour, and of the specific gravity 13·568.
When heated to about 660° F. it sublimes, and on cooling it condenses unchanged. If this experiment is made in a small glass tube, the metal forms a white ring of brilliant globules, which may be made to coalesce into a single large one. In this way its physical properties may be recognised, though the quantity is exceedingly minute.
Two oxides of this metal, a protoxide and peroxide, exist in combination with acids. A bluish-gray or grayish-black protoxide is separated from the salts of the protoxide by the fixed alkalis. The peroxide has an orange-red colour, and is the common red precipitate of the apothecary. Mercury unites with sulphur in two proportions. The proto-sulphuret, which is black, is formed from the salts of the protoxide by the action of sulphuretted-hydrogen: the bisulphuret is the well known pigment, cinnabar or vermilion. Mercury likewise unites with chlorine in two proportions, forming an insoluble protochloride and a soluble bichloride, the former calomel, the latter 290corrosive sublimate. It likewise unites with cyanogen. Mercury also unites in the state of protoxide and peroxide with the acids. Several compound salts are known to the chemist, but few occur in commerce or the arts.
Among the compounds resulting from the action of this metal with other substances, those which require notice in a toxicological treatise are the following:—1. The binoxide or red precipitate; 2. The bisulphuret or vermilion; 3. The protochloride or calomel; 4. The bichloride or corrosive sublimate; 5. The sulphate or Turbith mineral; 6. The bicyanide or prussiate of mercury; and 7. The nitrates of mercury. Its other compounds are of little consequence to the toxicologist.
1. Of Red Precipitate.
Red precipitate, when well prepared, is in the form of fine powder or small, brilliant, heavy scales of a scarlet or orange colour. It consists of 101 mercury and 8 oxygen. It is insoluble in water.
It is easily distinguished from all other substances by the action of heat. If a little of it is heated in a small glass tube, it becomes dark brown, and on cooling recovers its original colour. But if the heat be raised higher, metallic globules are sublimed, and oxygen gas is disengaged. The escape of oxygen may be ascertained by plunging to the bottom a small bit of burning wood, when the combustion will be observed to be enlivened.
2. Of Cinnabar.
Cinnabar or vermilion, the bisulphuret of mercury, usually exists in the arts in the form of a fine, heavy, red powder, of a peculiar tint, which is termed from this substance vermilion-red. In mass its structure is coarsely-fibrous, and its colour reddish-brown; and it has some lustre. When thrown down from a solution of corrosive sublimate by sulphuretted-hydrogen, or the alkaline hydrosulphates, it forms a black powder, which acquires a red tint by being sublimed. It is composed of 101 metal and 16 sulphur.
It is distinguished from other substances by the operation of heat, and by the effects of reduction with iron filings. Heated alone in a tube it sublimes without change. Its colour, indeed, which is fugacious under heat unless particular manipulations are used, becomes darker and dingy; but its lustre and crystalline texture are retained. Heated with iron filings in a tube, it gives off globules of mercury; and the existence of sulphuret of iron in what remains may be proved by the escape of sulphuretted-hydrogen on the addition of diluted sulphuric acid.
3. Of Turbith Mineral.
The Turbith mineral, or subsulphate of the binoxide of mercury, exists in the form of a bright lemon-yellow, heavy powder. It is soluble in 2000 parts of water, and has an acrid taste.
291It may be known by the effects of heat. When heated in a tube, globules of mercury are sublimed, and at the same time sulphurous acid gas is disengaged, as may be ascertained by the smell. But a better method of proving the existence of sulphuric acid in it is to expose it to the action of a solution of caustic potass: The potass separates from it the brownish-yellow peroxide, and appropriates the sulphuric acid, which may be found in the solution by acidulating with nitric acid, and then adding hydrochlorate of baryta, when a heavy, snow-white precipitate of sulphate of baryta will form. The nitric acid used in this process must be quite pure, and free of sulphuric acid, which the acid of commerce often contains.
4. Of Calomel.
Calomel (muriate, mild muriate, chloride, protochloride of mercury), is commonly met with in the shops in the form of a heavy powder, having a faint yellowish-white colour, and no taste or smell. In mass it forms compact, fibrous, translucent, shining cakes of great density. It is insoluble in water.
It is distinguished by the effects of heat, and those of the solution of caustic potass. Heated in a tube it sublimes unchanged, and condenses in a crystalline or crumbly mass. The solution of caustic potass or soda turns it at once black, disengaging protoxide of mercury and acquiring hydrochloric acid, the presence of which is proved by neutralizing the solution with nitric acid, and adding nitrate of silver, when a heavy white precipitate is formed, the chloride of silver. In applying this process, care must be taken to employ potass quite free of muriates, and nitric acid free of muriatic acid. Ammonia also renders calomel powder black, but the action and product are much more complex in their nature.
5. Of Corrosive Sublimate.
Corrosive sublimate (oxymuriate, corrosive muriate, bichloride of mercury), is by far the most important of the mercurial poisons, as it is both the most active of them, and the one most frequently used for criminal purposes. It is commonly met with in the form of a heavy, snow-white powder, or of small, broken crystals, or in white, compact, concave, crystalline cakes. It is permanent in the air; but in the sunshine is slowly decomposed, a gray insoluble powder being formed. It readily crystallizes, and the common form of the crystals is the quadrangular prism. Its specific gravity is 5·2. Its taste is strongly styptic, metallic, acrid, and persistent; and its dust powerfully irritates the nostrils. It is soluble, according to Thenard, in 20, according to Orfila, in 11 parts of temperate water, and in thrice its weight of boiling water. Its solution faintly reddens litmus. It is more soluble in alcohol than in water, boiling alcohol dissolving its own weight, and retaining when it cools, a fourth part. It is also very soluble in ether, so that ether will remove it from its aqueous 292solution. Corrosive sublimate may become the subject of a medico-legal analysis in three states. It may be in the solid form; it may be dissolved in water along with other mineral substances; and it may be mixed with vegetable and animal fluids or solids.
Of the Tests for Corrosive Sublimate in the solid state.
Corrosive sublimate in the solid state is distinguished from other substances by the action of the heat, and the effects of solution of caustic potass. Subjected to heat alone it sublimes in white acrid fumes; and if the experiment is made in a little tube, it condenses again unaltered in a crystalline cake. Treated with solution of caustic potass, it becomes yellow, the binoxide being disengaged, and hydrochloric acid uniting with the potass, as may be proved by nitrate of silver, after filtration and neutralization with nitric acid. The yellow colour of the binoxide which is separated in this process distinguishes corrosive sublimate from calomel, which is also decomposed by the potass solution, but yields a black protoxide. Caustic soda has the same effect. Not so caustic ammonia: Ammonia blackens calomel, but does not change the colour of corrosive sublimate, as it forms with it a white triple salt, commonly called white precipitate.
The process here described is the best and simplest method of determining chemically the nature of corrosive sublimate in its solid state. But two other tests may also be mentioned, as they have been a good deal used. A very good test is the process of reduction with potass, by which globules of mercury are sublimed, and a chloride of potassium left in the flux, as may be proved by the action of nitrate of silver on the solution of the flux previously neutralized with nitric acid. This test alone will not distinguish corrosive sublimate from calomel: The solubility of the former must be taken into account.—Another satisfactory test is the solution of protochloride of tin. Corrosive sublimate, when left for some time in this solution, first becomes grayish-black, and ere long its place is supplied by globules of mercury,—the chlorine being entirely abstracted by the protochloride of tin, which consequently passes to the state of a bichloride. Calomel is similarly affected.
Of the Tests for Corrosive Sublimate in a state of Solution.
Two processes may be mentioned for the detection of corrosive sublimate in mineral solutions,—a process by reduction, and a process by liquid tests.
Reduction process.—In order to procure mercury in its characteristic metallic state from a solution of corrosive sublimate, the following plan of procedure will be found the most delicate and convenient. Add to the solution, previously acidulated with hydrochloric acid if very weak, a little of the protochloride of tin, which will be seen presently to be a liquid reagent of great delicacy. If the solution is not darkened there is not present an appreciable quantity of mercury. 293If mercury is present a bluish-gray or grayish-black precipitate falls down, owing to the chemical action already particularized. After ebullition, this precipitate is to be allowed to subside, first in a tall glass vessel suited to the quantity of the solution, and afterwards in the small glass tube, Fig. 7, the superincumbent fluid being previously decanted off as far as possible. After it has subsided in the tube, the remaining fluid is withdrawn with the pipette, Fig. 8; water is poured over it; and this is withdrawn again after the precipitate has subsided a third time. The bottom of the tube is then cut off with a file, and the moisture which remains is driven off with a gentle heat. When this is accomplished, the powder, which is nothing else than metallic mercury, sometimes runs into globules. Should it not do so, the bit of tube is to be broken in pieces and heated in the tube, Fig. 1, when a brilliant ring of fine globules will be formed. If the globules are too minute to be visible to the naked eye, the tube is to be cut off with the file close to the ring; and the globules may then be easily made to coalesce into one or more of visible magnitude by scraping the inside of the tube with the point of a penknife.
This process is not recommended as preferable to the plan by liquid reagents which is next to be mentioned, and which is both more easily put in practice, and at the same time quite as satisfactory. It is related chiefly because it forms the ground-work of a process for detecting mercury in mixed animal or vegetable fluids. It will be remarked that the process does not prove with what acid the mercury was combined in the solution. But this is a defect of little consequence; for the only other soluble salts of mercury ever met with in the arts, namely, the nitrate, acetate, and cyanide, are too rare to be the source of any material fallacy; and are besides all equally poisonous with corrosive sublimate.
Process by Liquid Tests.—The process by liquid reagents consists in the application of several tests to separate portions of the solution. The tests which appear to me the most satisfactory are hydrosulphuric acid gas, hydriodate of potass, protochloride of tin, and nitrate of silver.
1. Hydrosulphuric acid gas transmitted in a stream through a solution of corrosive sublimate causes a dark, brownish-black precipitate, the bisulphuret of mercury. When the solution is not very diluted, the gas forms a whitish or yellowish precipitate before the blackening commences,—an effect which, according to Pfaff, distinguishes the salts of the peroxide of mercury from all other metals that are thrown down black from their solutions by sulphuretted-hydrogen.[835] The cause of this is that the particles of sulphuret first formed acquire a thin covering of corrosive sublimate by that property which chemists of late have termed superficial attraction. Hydrosulphuric acid is a very delicate test of the presence of mercury. It will detect corrosive sublimate, where its proportion is only a 35000th of the solution.[836]
294This test is not alone sufficient, unless reliance be placed on Pfaff’s criterion, which is rather a trivial one; for hydrosulphuric acid occasions a black precipitate in other metallic solutions, for example, in solutions of lead, copper, bismuth and silver. In mixed organic fluids its action is not liable to be prevented; but the precipitate formed is often kept intimately suspended, as in the instance of milk. It may be conveniently used in the form of hydrosulphate of ammonia. This test produces a dark-brown precipitate, which is said to pass slowly to a bright cinnabar red; but I have not been able to observe any transformation of the kind.
Hydriodate of Potass causes in solutions of corrosive sublimate a beautiful pale scarlet precipitate, which rapidly deepens in tint. The precipitate is the biniodide of mercury. This is a test of great delicacy when skilfully used, as it acts where the salt forms only a 7000th of the solution (Devergie). Care must be taken, however, not to add too much of the test, because the precipitate is soluble in an excess of the hydriodate, or too little, because the precipitate is also soluble in a considerable excess of corrosive sublimate.
The action of hydriodate of potass is not liable to any important ambiguity: no other iodide resembles in colour the biniodide of mercury. It is not a certain test, however, when other salts exist in solution along with corrosive sublimate. Chloride of sodium, nitrate of potass, and probably also other neutral salts possess the power of dissolving the precipitate. Sulphuric and nitric acids, even considerably diluted, oxidate and dissolve the mercury, and disengage iodine, which colours the fluid reddish-brown. When corrosive sublimate is dissolved in coloured vegetable infusions or animal fluids, the hydriodate of potass cannot be relied on, the colour of the precipitate being altered, as in infusion of galls, or the action of the test being suspended altogether, as by milk.
Protochloride of Tin causes first a white precipitate, which, when more of the test is added, gives place to a grayish-black one. In very diluted solutions the colour struck is grayish or grayish-black from the beginning. In such solutions Devergie has found it useful to acidulate with hydrochloric acid before adding the test. The chemical action here is peculiar. The white powder thrown down at first is protochloride of mercury; a part of the chlorine of the bichloride of mercury having been abstracted by the protochloride of tin, which becomes in consequence the bichloride. On more of the test being added these changes are repeated, the chlorine is removed from the protochloride of mercury, and metallic mercury falls down. This test is one of extreme delicacy, affecting solutions which contain only an 80,000th of salt. It is prepared by acting on tin powder or tinfoil with strong hydrochloric acid aided by a gentle heat. The solution must be kept carefully excluded from the air; otherwise bichloride of tin is formed, which does not act at all on the solution of corrosive sublimate.
The protochloride of tin is not liable to any fallacy. Neither is it 295liable to be suspended in its action by the co-existence of other saline substances. It causes precipitates with almost all animal and most vegetable fluids. But when corrosive sublimate is present, even in very small proportion, the precipitate is always darker than when no mercurial salt exists in solution, and frequently has its proper grayish-black tint. This property, as will presently be seen, is the foundation of a process for the detection of mercury in all states of admixture with organic matters.
Nitrate of Silver causes a heavy white precipitate, the chloride of silver, which darkens under exposure to light. This is a test for the chlorine of the corrosive sublimate, but not for the mercury, and is a necessary addition to the three former tests in order to determine how the mercury is kept in solution. It acts with very great delicacy.
It is of no use, however, when chlorine or hydrochloric acid is present either free or combined with other bases. It is not of use, therefore, in animal fluids and vegetable infusions, because very many of them, besides organic principles which form white precipitates with this test, contain a sensible proportion of hydrochlorate of soda.
Although the preceding liquid reagents when employed conjunctly are amply sufficient for determining the presence of corrosive sublimate in a fluid, many other tests hardly less characteristic and delicate have been used by medical jurists. These will now be shortly mentioned.
1. Lime-Water throws down the binoxide of mercury in the form of a heavy yellow powder. The precipitate first thrown down is lemon-yellow, an additional quantity of the test gives it a reddish-yellow tint, and a still larger quantity restores the lemon-yellow. This test is characteristic, but not so delicate as those already mentioned.—2. Caustic Potass has precisely the same effect as lime-water, except that the tint of the precipitate is always yellow—3. Caustic Ammonia causes a fine, white, flocculent precipitate of intricate composition, commonly called precipitate. It is a very delicate test; but ammonia likewise causes a white precipitate in other metallic solutions.—4. Carbonate of Potass causes a brisk-red precipitate, by virtue of a double decomposition, the precipitate being carbonate of mercury.—5. The Ferro-cyanate of Potass causes at first a white precipitate, the ferro-cyanide of mercury. The precipitate becomes slowly yellowish, and at length pale-blue, owing, it is believed, to the admixture of a small quantity of iron with the corrosive sublimate.—6. A polished plate of Copper immersed in a solution of corrosive sublimate becomes in a few seconds tarnished and brownish; and in the course of half an hour a grayish-white powder is formed on its surface. This powder, according to Orfila,[837] is a mixture of calomel, mercury, and a copper amalgam. If it is wiped off, and the plate then rubbed briskly where tarnished, it assumes a white argentine appearance.—7. A little Mercury put into a solution of corrosive sublimate is instantly tarnished on the surface; the solution in a few 296seconds becomes turbid, a heavy grayish precipitate is formed, and in no long time with the aid of agitation the whole corrosive sublimate is removed from the solution. The powdery precipitate is a mixture of finely divided mercury and calomel; the former being derived from the surface of the mercury, and the latter produced by the corrosive sublimate uniting with a larger proportion of the metal to form the protochloride.—8. A solution of Albumen causes a white precipitate, which is soluble in a considerable excess of the reagent. The nature of this precipitate will be discussed presently.—A slip of Gold aided by galvanism, becomes silver-white in the solution, in consequence of the formation of an amalgam. When the solution is concentrated, it may be thus tested by simply putting a few drops on a bit of gold, and touching the gold through the solution with an iron point, as recommended by Mr. Sylvester and Dr. Paris.[838] When the solution is very weak, a different method is necessary, and a process for the purpose has been proposed by M. Devergie, which appears so delicate, accurate, and at the same time simple, a mode of detecting traces of mercury in very weak solutions, as to deserve detailed notice. A thin plate of gold, and another of tin, a few lines broad, and two or three inches long, being closely applied to one another by silk threads at the ends, and then twisted spirally, this galvanic pile is left for twenty-four or thirty-six hours in the solution previously acidulated with muriatic acid; upon which the gold is found whitened, and mercury may be obtained in globules by heating the gold in a tube. Distinct indications may be obtained by this method, where the corrosive sublimate forms but an 80,000th of the water.[839] For facility of application, an important condition is, that the quantity of fluid should not exceed three or four ounces, because in a larger quantity the pile of the size stated above cannot remove the whole mercury. Somewhat similar to this is the galvanic method of Mr. Davy of Dublin. He proposes to place the suspected solution in a platinum crucible with hydrochloric acid, diluted with its own weight of water, to excite galvanic action by immersing in the fluid a plate of zinc, and to sublime and collect the reduced mercury, by washing the crucible, heating it over a spirit-lamp, and condensing the mercurial vapours on a plate of glass placed over the mouth of the crucible.[840]
Of the Tests for Corrosive Sublimate when mixed with Organic Fluids and Solids.
The process for detecting corrosive sublimate in mixtures of organic fluids and solids, such as the contents of the stomach, is now to be described. But some remarks are previously required on the chemical relations subsisting between this poison and various principles of the vegetable and animal kingdoms.
297These relations are important in a medico-legal point of view on several grounds. On the one hand, the chemical changes which corrosive sublimate undergoes often alter so much the action of its tests, as to render necessary a process of analysis materially different from any hitherto described. And on the other hand, these chemical changes, of which some take place rapidly, others slowly, will hinder the corrosive sublimate, more or less completely, from exerting its usual operation on the animal system; so that it may thus either accidentally fail to act as intended, or be checked in its operation by antidotes administered for the purpose.
It appears from the researches of M. Boullay, confirmed by those of Professor Orfila, that various vegetable fluids, extracts, fixed oils, volatile oils and resins, possess the power of decomposing corrosive sublimate. According to M. Boullay, a part of the chlorine is gradually disengaged in the form of hydrochloric acid, and the salt is consequently converted into calomel, which is deposited in a state of mixture or combination with vegetable matter.[841] Some vegetable fluids produce this change at once, others not for some hours, others not for days, and only when aided by a temperature approaching ebullition. For example, a strong infusion of tea, mixed with a solution of a few grains of corrosive sublimate, becomes immediately muddy, and an insoluble cloud separates in half an hour. But the remaining fluid slowly becomes muddy again, and in eight days a considerable precipitate is formed. Both precipitates contain mercury; the former, I find, contains 31 per cent. On the other hand, an infusion of galls in like circumstances does not become muddy for six or seven hours. A solution of sugar does not undergo any change after being mixed with a solution of corrosive sublimate for months at the ordinary temperature of the atmosphere; but at the temperature of ebullition Boullay has found that the usual changes ensue, though to no great extent.
The experiments of Professor Taddei of Florence have farther shown, that the property of decomposing corrosive sublimate is possessed in an eminent degree by one of the vegetable solids, gluten. If the salt in solution is properly mixed with a due proportion of gluten of wheat, that is, about four times its weight, the water will be found no longer to contain any mercury, while the gluten becomes whitish, brittle, hard, and not prone to putrefaction. A ternary compound is formed, the protochloride of mercury and gluten.[842] This change is effected with rapidity.
The researches of Berthollet,[843] repeated and extended by Professor Orfila,[844] have also shown that the same property is possessed by most animal fluids and solids. Among the soluble animal principles, albumen, caesin, osmazôme, and gelatin possess it in a high degree, but above all albumen, the action of which has been examined with 298some care, as it supplies the physician with the most convenient and effectual antidote against the effects of the poison.
If a solution of albumen, for example that procured by beating white of eggs in water, is dropped by degrees into a solution of corrosive sublimate, a white flaky precipitate is immediately thrown down, which when separated and dried forms horny masses, hard, brittle, and pulverizable. The precipitate is soluble in a considerable excess of albumen; so that wherever albumen abounds in any fluid, to which corrosive sublimate has been added, a portion of the mercury will always be found in solution. The precipitate is also soluble in a considerable excess of corrosive sublimate. The dry precipitate I have found to contain 6 per cent. of metallic mercury.
The action of casein as it exists in milk is precisely the same. A solution of corrosive sublimate, poured into a large quantity of milk, causes no change; but if the proportion of salt be considerable, a flaky coagulum is formed, and the milk becomes clear. The principles, osmazôme and gelatin, are similar in their effects, though not quite so powerful. Urea has no chemical action with corrosive sublimate. Of the compound animal fluids, blood and serum have the same effects as albumen.
Many insoluble animal principles, as well as all the soft solids of the animal body, act in the same manner with vegetable gluten. Fibrin, for example, coagulated albumen, or coagulated casein, acts precisely in the same way. Muscular fibre, the mucous and serous membranes, the fibrous textures, and the brain, have all the same effect: they become firmer, brittle, white, and a white powder detaches itself from their surface, which contains mercury and animal matter. This chemical action, which Taddei has proved to take place in the living[845] as well as in the dead body, is the source of the corrosive property of the poison, as was first pointed out by Berthollet in his essay formerly quoted.
In all of the compounds thus formed by vegetable and animal substances, the presence of mercury is easily proved by boiling the powder in a solution of caustic potass. The organized matter is dissolved; a heavy, grayish-black powder is formed, which is protoxide of mercury; and if this be collected in the way formerly described, it forms running quicksilver when heated.
A difference of opinion prevails as to the nature of the changes effected by the mutual action of corrosive sublimate and organic matter. For example, in the instance of the action of albumen, which has been most carefully examined, Berzelius and Lassaigne[846] regard the precipitate as a compound of bichloride of mercury with albumen. Professor Rose and Dr. Geoghegan[847] have proved it, in their opinion, to be a compound of binoxide of mercury and albumen without any chlorine. And according to Boullay it is composed of albumen 299in union with calomel.[848] Lassaigne says he has found it to be a compound of ten equivalents of albumen with one of mercury, or 93·33 per cent. of the former, and 6·67 of the latter.[849] The compound with fibrin he considers to be analogous in composition.
With regard to the changes induced by these effects of organized matter on the operation of the liquid tests for corrosive sublimate, it will in the first place be manifest that the poison may thus be wholly removed from their sphere of action: it may be thrown down as an insoluble substance, on which any process by liquid tests hitherto mentioned will of course fail to act. But secondly, even when a moderate quantity does remain in solution, the operation of the liquid tests, as formerly noticed under the head of each, will be materially modified. It is of some moment for the medical jurist to remember, that by reason of the slowness with which the changes in question sometimes takes place, the poison may exist abundantly in solution at one time, and yet be present only in small quantity after an interval of some hours or days.
Process for Organic Mixtures.—Various processes have been proposed for detecting corrosive sublimate in organic mixtures. The first I shall mention is one proposed by myself in former editions of this work. It is a double one; of which sometimes the first part, sometimes the second, sometimes both may be required. The first removes the corrosive sublimate undecomposed from the mixture, which may be accomplished when its proportion is considerable; the second, when the proportion of corrosive sublimate is too small to admit of being so removed, separates from the mixture metallic mercury; and the analyst will know which of the two to employ by using the protochloride of tin as a trial-test in the following manner.
A fluid mixture being in the first instance made, if necessary, by dividing and bruising all soft solids into very small fragments, and boiling the mass in distilled water, a small portion is to be filtered for the trial. If the protochloride of tin causes a pretty deep ash-gray or grayish-black colour, the first process may prove successful; if the shade acquired is not deep, that process may be neglected, and the second put in practice at once.
First branch of the Process.—In order to remove the corrosive sublimate undecomposed, the mixture, without filtration, is to be agitated for a few minutes with about a fourth part of its volume of sulphuric ether; which possesses the property of abstracting the salt from its aqueous solution. On remaining at rest for half a minute or a little more, the etherial solution rises to the surface, and may then be removed by suction with the pipette (Fig. 8). It is next to be filtered if requisite, evaporated to dryness, and the residue treated with boiling water; upon which a solution is procured that will present the properties formerly mentioned as belonging to corrosive sublimate in its dissolved state. This branch of the process is derived from one of Orfila’s methods.
Second branch of the Process.—If the preceding method should 300fail, or shall have been judged inapplicable, as will very generally be the case, the mixture is to be treated in the following manner. In the first place, all particles of seeds, leaves, and other fibrous matter of a vegetable nature, are to be removed as carefully as possible. This being done, the mixture, without undergoing filtration, is to be treated with protochloride of tin as long as any precipitate or coagulum is formed. If there were solid animal matters in the mixture, besides being cut and carefully bruised as directed above, they should also be brought thoroughly in contact with the salt of tin by trituration. The mixture, even if it contains but a very minute proportion of mercury, will acquire a slate-gray tint, and become easily separable into a liquid and coagulum. The coagulum is to be collected, washed and drained on a filter; from which it is then to be removed without being dried; and care should be taken not to tear away with it any fibres of the paper, as these would obstruct the succeeding operations. The mercury exists in it in the metallic state for reasons formerly mentioned.
The precipitate is next to be boiled in a moderately strong solution of caustic potass contained in a glass flask, or still better in a smooth porcelain vessel glazed with porcelain; and the ebullition is to be continued till all the lumps disappear. The animal and vegetable matter, and oxide of tin united with them, will thus be dissolved; and on the solution being allowed to remain at rest, a heavy grayish-black powder will begin to fall down in a few seconds. This is chiefly metallic mercury, of which, indeed, globules may sometimes be discerned with the naked eye or with a small magnifier.
In order to separate it, leave the solution at rest under a temperature a little short of ebullition for fifteen or twenty minutes, or longer, if necessary. Fill up the vessel gently with hot water without disturbing the precipitate, so that a fatty matter, which rises to the surface in the case of most animal mixtures, may be skimmed off first with a spoon, and afterwards with filtering paper. Then withdraw the whole supernatant fluid, which is easily done on account of the great density of the black powder. Transfer the powder into a small glass tube, and wash it by the process of affusion and subsidence till the washings do not taste alkaline. Any fibrous matter which may have escaped notice at the commencement of the process, and any lumpy matter which may have escaped solution by the potass, should now be picked out. The black powder is the only part which should be preserved. If the quantity of powder is very minute, an interval of twelve hours should be allowed for each subsidence, and the tube represented in Fig. 7 should be used.
Lastly, the powder is to be removed, heated, and sublimed, as in the last stage of the process described in page 293, for detecting corrosive sublimate in a pure solution.
The second branch of this process is very delicate. I have detected by it a quarter of a grain of corrosive sublimate mixed with two ounces of beef, or with five ounces of new milk, or porter, or tea made with a liberal allowance of cream and sugar. I have also 301detected a tenth part of a grain in four ounces of the last mixture, that is in 19,200 times its weight.
It may be applied successfully and without difficulty to a very large majority of medico-legal cases. The only difficulty in the way of applying it to all organic mixtures whatever arises from the occasional presence of some vegetable matters, such as seeds, leaves, ligneous fibre and the like, which are insoluble in caustic potass, and which may therefore be left behind with the mercurial precipitate, and obstruct the subsequent sublimation of the metal. This difficulty may be sometimes got rid of, as recommended above, by picking such matters out of the mixture before the protochloride of tin is added. No mercury is lost by so doing, for none of it is united with these vegetable matters: corrosive sublimate does not form any chemical compound with them as it does with other vegetable matters soluble in caustic potass, and with the soft animal solids. When the particles are too small to admit of being thus removed, or cannot be afterwards removed during the process of washing the black powder, which is left after the action of potass—the analyst must be content with the increased facility of sublimation derived from the abstraction of other vegetable and animal admixtures, and take care to use a tube of greater length and with a larger ball than usual. If the sublimate is too much obscured by empyreumatized matter to exhibit distinctly its metallic, globular appearance, the portion of the tube is to be broken off, and scraped, washed, and boiled with a little rectified spirit in a tube. If the globules do not then become visible, a second sublimation will render them distinct. This supplemental operation, however, will be very seldom required; and the process given above will be found to apply to a great majority of instances.
Various objections brought against this process by reviewers and others were noticed in previous editions of this work. The result of the investigation is, that, though not by any means a perfect process, it is one of the most convenient and certain, and least fallacious of all yet proposed. The first step for separating corrosive sublimate by ether in the undecomposed state,—which is borrowed from a suggestion of Professor Orfila, will seldom succeed; for the poison is seldom present in sufficient quantity.
It must be observed that this as well as every other method yet proposed for discovering corrosive sublimate in compound mixtures merely indicates the presence of mercury, and does not point out its state of combination. More especially, in the case of the contents of the stomach, if mercury be not obtained from the filtered fluid, it is impossible to know whether what is detected in the solid matter only may not have proceeded from calomel given medicinally. This objection can be obviated solely by sufficient evidence that calomel was not administered; at least the different criterions laid down by Professor Orfila for distinguishing calomel in the alimentary canal from the products of the decomposition of corrosive sublimate do not appear sufficiently precise, or commonly applicable.[850]
302Various processes for detecting corrosive sublimate in organic mixtures have been proposed by others. But none of these seem to me preferable to the method detailed above, with the exception of one which has been lately proposed by Professor Orfila, and which is particularly deserving of notice, because, although complex, he has found it sufficiently manageable and delicate for detecting mercury in the animal textures and secretions, into which it has obtained admission through the medium of absorption in cases of poisoning with the compounds of mercury. Like the previous process, however, it merely detects mercury, and cannot point out the state of combination in which mercury was administered, or mixed with the substance examined.
If the suspected matter be sufficiently liquid, boil for a few minutes and filter; acidulate the product with a few drops of hydrochloric acid; and immerse some slips of copper-leaf in it for a few hours. Should they be tarnished, dissolve oxide and chloride of copper from the surface by means of ammonia; wash them and press them between folds of filtering paper; cut them in pieces, and heat these in a glass tube. Globules of mercury may be obtained or not. In either case, let the liquid, in which the plates were first immersed, be evaporated to dryness over the vapour-bath; add to the residue a sixth of sulphuric acid in a retort with a receiver; and heat gently till a nearly dry carbonaceous mass be obtained. Boil this with an ounce and a half of nitro-hydrochloric acid [Edin. Pharm.], until the charcoal be again nearly dry. Heat what remains with boiling distilled water, filter, apply to a small part of the liquid the copper test as just described, and try whether corrosive sublimate can be detached from the remainder by means of sulphuric ether (p. 299). The distilled fluid in the receiver may contain corrosive sublimate in considerable proportion, relatively to what existed in the subject of analysis. In order to discover it, boil the liquid for fifteen minutes with nitro-hydrochloric acid; transmit chlorine gas for an hour, filter, and evaporate to dryness over the vapour-bath; dissolve the residue in water, and search for corrosive sublimate both by copper plates, and by agitation with ether.
If mercury be not thus detected, proceed to the solid matter left on the filter, by which the subject of analysis was in the first instance separated into a liquid and solid part. Examine this by evaporation to dryness over the vapour-bath, and charring with sulphuric acid in a retort with a receiver attached; and then subject the product to the same steps as those detailed above for the dried residuum of the liquid part.
If the materials for analysis be soft solids, especially the stomach, intestines, liver, and the like, commence at once with the process of charring with sulphuric acid. In the case of the urine, examine both the liquid and sediment. Filter the liquid, transmit chlorine to excess, let the product rest twenty-four hours, filter, evaporate to dryness, dissolve the residue in water acidulated with hydrochloric acid, and test the solution both with copper-leaf and by agitation with ether. Heat the sediment with nitro-hydrochloric acid as 303directed above, and then proceed as with the liquid portion of the urine.[851]
Some other processes, but probably inferior to that of Professor Orfila, will be found in the last edition of this work. It seems unnecessary to reproduce them here.
6. Of Bicyanide of Mercury.
The bicyanide of mercury is a compound of mercury and cyanogen. It is usually sold in the form of white, opaque, heavy, crystals, which are rhomboidal prisms. It has a disagreeable, corrosive, metallic taste. It is easily known from every other substance by the effects of heat. If a small quantity of it, previously well dried, be introduced into a glass phial to which a small tube is fitted by means of a cork, on the application of heat the salt becomes black; mercury is sublimed, and condenses in globules on the upper part of the phial; and a gas escapes, which has the odour of prussic acid, and burns with a beautiful rose-red flame.
7. Of the Nitrates of Mercury.
The nitrates of mercury are used in some of the arts, but have so rarely been the cause of injury to man that they are of little medico-legal importance. I am acquainted with only one case of poisoning with them.[852]
There are two nitrates, the protonitrate and pernitrate. 1. The protonitrate is in transparent colourless crystals, entirely soluble in water with the aid of a slight excess of nitric acid; and the solution is precipitated black by the alkalis, black by sulphuretted-hydrogen, white by muriatic acid, and yellow by hydriodate of potass. The crystals when heated discharge fumes of nitrous acid, and when the whole acid is driven off the red oxide is left, which by farther heat is converted into metallic mercury. 2. The pernitrate is similarly affected by heat. Its crystals form white or yellowish needles. Water decomposes them, separating an insoluble yellowish subnitrate, and dissolving a supernitrate, which is precipitated yellow by the alkalis, black by sulphuretted-hydrogen, carmine-red by the hydriodate of potass. Copper separates mercury from both nitrates; and so does gold or platinum when aided by a galvanic current.
Section II.—Of the mode of Action of Mercury and the Symptoms it excites in Man.
The effects of mercury on the animal body are more diversified than those of any other poison. It acts on a great number of important organs, and in consequence the phenomena of its action are proportionately various. It is not surprising, therefore, that some 304ambiguity still prevails as to its mode of action and the circumstances by which the action is regulated.
The attention of toxicologists in their physiological researches has been chiefly turned to the more active preparations of mercury, and especially to corrosive sublimate, when given in such quantity as to prove fatal in a few days at farthest. The more immediate and prominent properties of corrosive sublimate have consequently received some elucidation. But its qualities as a slow poison, as well as the analogous operation of the less active compounds of mercury, have not been experimentally examined with the same care: indeed it is questionable whether the phenomena of the latter description as they occur in man can be studied with much advantage by means of experiments on animals.—In treating of the mode in which the compounds of mercury act, the most convenient method will be to consider at present its action in the form of corrosive sublimate in large doses as ascertained by late experiments, and to reserve the consideration of the general action of mercurial poisons at large till their effects on man have been fully described.
The mode of action of corrosive sublimate has been examined particularly by Sir B. Brodie in 1812;[853] by Dr. Campbell in 1813,[854] by M. Smith in 1815,[855] by M. Gaspard in 1821,[856] and more lately by Professor Orfila.[857] The following is a short analysis of their experiments and results.
The leading phenomena remarked by Sir B. Brodie, on large doses being introduced into the stomach, were very rapid death, corrosion of the stomach, and paralysis of the heart. In rabbits and cats, from six to twenty grains, injected in a state of solution into the stomach, produced in a few minutes insensibility and laborious breathing, then convulsions, and death immediately afterwards,—the whole duration of the poisoning varying from five to twenty-five minutes. After death the inner membrane of the stomach was gray, brittle, and here and there pulpy,—changes precisely the same with those produced by corrosive sublimate on the dead stomach. When the chest was opened immediately after death, the heart was found either motionless or contracting feebly; and in both circumstances the blood in its left cavities was arterial.
These experiments make it evident that the brain was acted on as well as the heart, and that the immediate cause of death was stoppage of the heart’s action. But they do not show whether the action takes place through absorption, or by a primary nervous impression transmitted along the nerves.
I am not acquainted with any other experiments of consequence on the operation of corrosive sublimate when introduced into the alimentary canal. But some interesting observations have been made by Campbell, Smith, Gaspard, and Orfila severally as to its effects 305when applied to the cellular tissue or injected at once into the blood of a vein. It follows from their researches, taken along with those of Sir B. Brodie, that, like arsenic, corrosive sublimate is an active poison, to whatever part or tissue in the body it is applied.
Campbell, Smith, and Orfila all agree in assigning to it dangerous properties, when it is applied to a wound or the cellular tissue of animals. Even in the solid state, and in the dose of three, four, or five grains only, it causes death in the course of the second, third, fourth, or fifth day. The symptoms antecedent to death are generally those of dysentery; and corresponding appearances are found after death, namely, redness, blackness, or even ulceration of the villous coat of the stomach and rectum, the intermediate part of the alimentary canal being sound. This poison, therefore, has, like arsenic, the singular power of inflaming the stomach and intestines, even when it is introduced into the system through a wound.
But this is not its only property in such circumstances. According to Smith and Orfila, it also possesses the power of inflaming both the lungs and the heart. Orfila found the lungs unusually compact and œdematous in some parts; and Smith observed on their anterior surface black spots, elevated in the centre, evidently the consequence of effusion of blood. As to the heart, in one of Smith’s experiments black spots were found in its substance, immediately beneath the lining membrane of the ventricles; and Orfila invariably found in one part or another of the lining membrane, most commonly on the valves, little spots of a cherry-red or almost black colour; nay, on one occasion he observed these spots so soft that slight friction made little cavities. The production of pneumonia by corrosive sublimate when applied to a wound appears well established; but the appearances assumed as indications of carditis are equivocal, since they may have arisen simply from dyeing of the membrane of the heart in the fluid part of the blood after death.
The researches of Gaspard were confined to the effects of the poison when injected at once into the blood. They show still more clearly its tendency to cause inflammation of the lungs; and they prove that through the channel of the blood, as through the cellular tissue, it is apt to cause inflammation of the stomach and rectum. The symptoms were vomiting, bloody diarrhœa, difficult breathing, apparent pain of chest, and bloody sputa; and death took place in a few seconds or in three or four days, according to the dose, which varied from one to five grains. The appearances in the dead body were principally redness in the mucous membrane of the intestines; and in the lungs, according to the length of time the animal survived, either black ecchymosed spots, or black tubercular masses, some inflamed, others gangrenous, others suppurated, or finally, regular abscesses separated from one another by healthy pulmonary tissue.[858]
Besides the effects mentioned in the preceding abstract, two of the experimentalists referred to have likewise observed in animals the same remarkable operation on the salivary organs which forms so 306conspicuous a feature in the action of the compounds of mercury on man. Dr. Campbell observed mercurial fetor, and M. Gaspard mercurial salivation. Another writer, Zeller, found that dogs might be made to salivate, but not graminivorous animals.[859] Schubarth, however, remarked profuse salivation in a horse, to which twenty-four ounces of strong mercurial ointment were administered in the way of friction in sixteen days:[860] and I observed the same symptoms in a rabbit on the sixth day after the commencement of daily mercurial inunction.
The result of the preceding inquiry is, that corrosive sublimate causes, when swallowed, corrosion of the stomach, and in whatever way it obtains entrance into the body, irritation of that organ and of the rectum, inflammation of the lungs, depressed action and perhaps also inflammation of the heart, oppression of the functions of the brain, inflammation of the salivary glands. These phenomena are diversified enough. But it will presently be found that other organs still are implicated in its effects on man.
Before proceeding, however, to its effects on man, some notice may be taken of a question, connected with its mode of action, which has long been the subject of controversy. The experiments already quoted render it probable that corrosive sublimate, before it can exert its remote action, must enter the blood; and the facts to be enumerated under the next head of the present section will render it probable that the milder compounds of mercury used in medicine also act in a similar manner. Physicians and chemists, therefore, long sought to discover this metal in the solids and fluids of the body while under its influence; and the failure of some attempts to detect it has naturally led to its presence throughout the system being called in question by many. This inquiry, besides its interest in a physiological point of view, is highly important in respect to medico-legal practice, since it forms a material branch of the general questions which at present occupy the attention of medical jurists,—whether poisons that act through the blood should be sought for by chemical analysis in other parts of the body besides the stomach, intestines, or other organ to which they have been directly applied—and in what particular quarters the search should be principally made.
In the case of mercury, the evidence of the absorption of the poison, and of its entering the tissues and secretions of the body, is now unimpeachable. This is chiefly derived from observations and experiments made on man and animals after the long-continued use of the milder preparations of mercury; it being imagined that if the poison enters the blood at all, the greatest quantity will be found under these circumstances. The facts may be arranged under three heads. Some relate to the discharge of metallic mercury from the living body during a mercurial course for medicinal purposes; others to the discovery of metallic mercury in the dead body after a mercurial 307course, and others to the detection of mercury by a careful chemical analysis in the fluids and solids during life or after death.
Many stories are related by the older authors of the discharge of running quicksilver from the living body during a mercurial course. Some of the most authentic of them have been collected by Zeller. In his list of cases it is stated that Schenkius met with an instance of the discharge of a spoonful of quicksilver by vomiting; that Rhodius twice remarked quicksilver pass with the urine; and that Hochstetter once saw it exhaled with the sweat.[861] Fallopius likewise states, that in people who had used mercurial inunction for three years, and who had the bones of the leg laid bare by suppurating nodes, he had seen quicksilver collected in globules on the tibia; and he speaks of its being the practice in his day to draw the mercury from the body, when overloaded with it, by successively amalgamating a bit of gold in the mouth and heating the amalgam to expel the mercury.[862] With regard to these statements of the older authors it may be observed that, although their singularity renders them questionable, they ought not to be rejected at once, as some have done, merely because corresponding facts have not been witnessed in modern times; for no one can now-a days have such opportunities for observation as were enjoyed by Fallopius and his contemporaries. The experiment of amalgamating gold in the mouth of a person under a course of mercury has always failed in modern times. But who can now have an opportunity of making the experiment during a mercurial course of three years? Besides, the statements quoted above are not all destitute of modern confirmation. Thus Fourcroy has noticed the case of a gilder attacked with an eruption of little boils, in each of which was contained a globule of quicksilver. Bruckmann mentions the case of a lady who subsequently to a course of mercury remarked after a dance many small black stains on her breast, and minute globules of quicksilver in the folds of her shift.[863] And Dr. Jourda has described in a late French periodical a case where fluid mercury was passed by the urine. The last fact appears satisfactory in all its circumstances. A patient had been taking corrosive sublimate for a month in the dose of a grain, besides using for the first sixteen days a gargle containing metallic mercury finely divided. Towards the close of the month he observed on the sill of the window, on which he used to turn up his chamber-pot after using it, many little globules of mercury, amounting in all to four grains. Dr. Jourda on learning this observation of his patient collected some of the urine with care, and after it had stood some time found in it a black, powdery sediment, which, when separated and dried, formed little globules of mercury.[864]
The next class of facts in favour of the entrance of mercury into 308the blood are derived from the discovery of the metal in the bodies of persons who had undergone a long mercurial course recently before death. In the German Ephemerides it is said that no less than a pound of it was found in the brain and two ounces in the skull-cap of one who had been long salivated.[865] This is certainly too marvellous a story. But analogous observations have been made lately. In Hufeland’s Journal it is mentioned that a skull found in a churchyard contained running quicksilver in the texture of its bones, and that there is preserved in the Lubben cabinet of midwifery a pelvis infiltered with mercury, and taken from a young woman who died of syphilis.[866] An unequivocal fact of the same nature has been related by Mr. Rigby Brodbelt. In a body of which he could not learn the history he found mercurial globules as big as a pin-head lying on the os hyoides, laryngeal cartilages, frontal bone, sternum, and tibia.[867] Another equally unquestionable fact of the kind has been supplied by Dr. Otto. On scraping the periosteum of several of the bones of a man who had laboured under syphilis, he remarked minute globules issuing from the osseous substance: in some places globules were deposited between the bone and periosteum, where the latter had been detached in the progress of putrefaction; and in other places, when the bones were struck, a shower of fine globules fell from them.[868] Wibmer observes that Fricke, surgeon to the Hamburg Infirmary, has obtained mercury by boiling the bones of persons who had been long under a course of mercurial inunction.[869]
The third and most satisfactory class of facts are the result of actual chemical analysis. These results were long variable. On the one hand, Mayer, Marabelli,[870] and Devergie,[871] failed to detect mercury in the fluids of people under a mercurial course; and I myself,[872] as well as Dr. Samuel Wright,[873] had no better success in some experiments on animals. On the other hand, Zeller detected it after death in the blood and bile, Cantu procured it from the urine, Buchner found it in the blood, saliva, and urine, and Schubarth extracted it from the blood. The first experimentalist found that in the blood and bile of animals killed by mercurial inunction, mercury could be detected by destructive distillation, but not by any fluid tests.[874] Cantu, by operating on sixty pounds of urine, taken from persons under the action of mercury, procured no less than twenty grains of the metal from the sediment.[875] The experiments of Buchner are very satisfactory. By destructive distillation of the crassamentum of seven ounces of blood taken from a patient who was salivated by mercury, he obtained 309rather more than a quarter of a grain of globules; two pounds of saliva yielded in the same way a 200th of a grain; and the urine contained so much that it became brownish-black with sulphuretted-hydrogen.[876] Buchner likewise adds, that Professor Pickel of Würzburg procured mercury by destructive distillation from the brain of a venereal patient who had long taken corrosive sublimate.[877] Not less satisfactory are the experiments of Dr. Schubarth. A horse after being rubbed for twenty-nine days with mercurial ointment to the total amount of eighty ounces, died of fever, emaciation, diarrhœa, and ptyalism. On the sixteenth day, when ptyalism had set in, a quart of blood was drawn from the jugular vein, and after death another quart was collected from the heart, great vessels and lungs,—extreme care being taken to collect it perfectly pure. In each specimen there was procured by destructive distillation a liquor, in which minute metallic globules were visible. A copper coin agitated in the liquor was whitened; and when the oily matter was separated by filtration and boiling in alcohol, the residue gave with nitric acid a solution, which produced an orange precipitate with hydriodate of potass.
These researches were considered adequate to prove the strong probability of the absorption of mercurial preparations when introduced into the animal. But the frequency with which negative results were obtained by competent inquirers, and in circumstances apparently favourable, threw an air of doubt over the positive facts, however clear they seem to be in themselves,—till at length Professor Orfila proved by a series of careful experiments that the cause of failure must generally have been the want of a process sufficiently delicate: for in all ordinary circumstances, by using his process described above, he succeeded in obtaining mercury in the urine and liver of animals poisoned with corrosive sublimate, as well as in the urine of patients who were taking that salt in medicinal doses. He could not detect it, however, in the blood.[878] Since these investigations, Professor Landerer of Athens detected mercury in the brain, liver, lungs and spinal cord of a man who poisoned himself with two ounces and a half of corrosive sublimate;[879] and M. Audouard has twice found it in the urine and once in the saliva of persons salivated with mercury, by simply transmitting chlorine, exposing the liquid to the air for a day, evaporating it nearly to dryness, dissolving the residue in water slightly acidulated with hydrochloric acid, immersing copper-leaf for twenty-four hours, and heating the stained portions in a tube.[880]
The cases of poisoning with the preparations of mercury, which have been observed in the human subject, may be conveniently arranged under three varieties. In one variety the sole or leading symptoms are those of violent irritation of the alimentary canal. 310In another the symptoms are at first the same as in the former, but subsequently become united with salivation and inflammation of the mouth, or some of the other disorders incident to mercurial erethysm, as it is called. In a third variety the preliminary stage of irritation in the alimentary canal is wanting, and the symptoms are from beginning to end those of mercurial erethysm in one or another of its multifarious forms.
The first variety of poisoning with mercury is remarked only in those who have taken considerable doses of its soluble salts, particularly corrosive sublimate. The second is produced by the same preparations. The third may be caused by any mercurial compound.
1. The symptoms in the first variety are very like what occur in the ordinary cases of poisoning with arsenic,—namely, vomiting, especially when any thing is swallowed, violent pain in the pit of the stomach, as well as over the whole belly, and profuse diarrhœa. But there exist between the effects of the two poisons some shades of difference which it is necessary to attend to.
In the first place,—taking corrosive sublimate as the best example of the preparations which cause this variety of poisoning with mercury,—the symptoms generally begin much sooner than those caused by arsenic. The symptoms of irritation in the throat may begin immediately, nay, even during the very act of swallowing;[881] and those in the stomach may appear either immediately,[882] or within five minutes.[883]
Secondly, the taste is much more unequivocal and strong. Even a small quantity of corrosive sublimate, either in the solid or fluid state, and considerably diluted, has so strong and so horrible a taste, that no one could swallow it in a form capable of causing much irritation in the stomach, without being at once made sensible by the taste that he had taken something unusual and injurious. Occasionally, indeed, persons thus warned of their danger while in the act of swallowing the poison, have stopped in time to escape fatal consequences.[884]
Thirdly, the sense of acridity which it excites in the gullet during the act of deglutition, and throughout the whole course of the subsequent inflammation of the alimentary canal, is usually much stronger. If the dose be not small, or largely diluted, or in the solid form, the sense of tightness, acridity, or burning in the throat and gullet during deglutition is often far greater than ever occurs at any stage in the instance of arsenic; and sometimes it is very severe even when corrosive sublimate is taken in the solid form.[885] The tightness and 311burning in the throat often continue throughout the whole duration of the poisoning; and may be so excessive as to cause complete inability to swallow,[886] or even to speak.[887] Occasionally the affection of the throat is the only material injury inflicted by the poison, as in a case related by Dr. J. Johnstone of a young woman, who tried to swallow two drachms of corrosive sublimate in the solid state, but was unable to force it down on account of the constriction it caused in the gullet. She died in six days of mortification of the throat.[888] The greater violence of the action of corrosive sublimate on the throat, compared with that of arsenic, is evidently owing to its greater solubility and powerful chemical operation on the animal textures.
Fourthly, instead of the contracted ghastly countenance observed in cases of poisoning with arsenic (but which, it will be remembered, is not invariable in that kind of poisoning), those who are suffering under the primary effects of corrosive sublimate have frequently the countenance much flushed, and even swelled.[889]
Corrosive sublimate seems to occasion more frequently than arsenic the discharge of blood by vomiting and purging,—obviously because it is a more powerful local irritant.
It likewise gives rise more frequently to irritation of the urinary passages. This irritation generally consists in frequent, painful micturition; but the secretion of urine is often suppressed altogether. Instances of this kind have been related by Mr. Valentine,[890] by my colleague, Professor Syme,[891] by an anonymous writer in the Medical and Physical Journal,[892] by Dr. Venables,[893] by Mr. Blacklock,[894] and by M. Ollivier, in whose case, however, the poison was the bicyanide of mercury.[895] In the last three cases the suppression was total, and continued till death; which did not ensue, in one till eight, in the next till five, and in the last till nine days after the poison was taken. Sometimes, as in Ollivier’s case, the urinary irritation is attended with symptoms of excitement of the external parts, such as swelling and blackness of the scrotum and erection of the penis.
Another distinction seems to be that corrosive sublimate is more apt than arsenic to cause nervous affections during the first inflammatory stage. The tendency to doze, which sometimes interrupts the inflammatory symptoms caused by arsenic, has been more frequently observed in cases of poisoning with corrosive sublimate.[896] The same may be said of tremors and twitches of the extremities. Sometimes the stupor approaches even to absolute coma;[897] and the twitches occasionally amount to distinct, nay violent convulsions.[898] In other instances paraplegia has been witnessed.[899]
312Another difference is, that the effects of mercurial irritants are fully more curable than those of arsenic. Recovery has taken place even after half an ounce was swallowed, with the effect of inducing both bloody vomiting and purging.[900] This may depend in part on the greater solubility of mercurial preparations, so that they are more easily discharged than arsenic, which often remains in the stomach after days of continual vomiting,—and in part on corrosive sublimate and other soluble salts of mercury being converted, in no long time and much more easily, into comparatively innocuous compounds, either by antidotes intentionally given for the purpose, or by animal principles in the secretions and accidental contents of the alimentary canal.
Lastly, deviations from the ordinary course and combination of the symptoms appear to be more rare in the instance of corrosive sublimate than in that of arsenic.
To these general statements, it may be right to add the heads of one or two actual cases, lest an exaggerated idea be conveyed of the combination of the symptoms as they usually occur. For this purpose it will be sufficient to refer to a fatal case related by M. Devergie, to an instance of recovery, without salivation having supervened, which is contained in Orfila’s Toxicology, and to another by Dr. Vautier, presenting the mildest possible symptoms of this variety. In Devergie’s case, the patient, a female, swallowed three drachms of corrosive sublimate in solution, and was soon after seized with vomiting, purging, and pain in the belly. In five hours, when she was first seen by Devergie, the skin was cold and damp, the limbs relaxed, the face pale, the eyes dull, and the expression that of horror and anxiety. The lips and tongue were white and shrivelled; and she had dreadful fits of pain and spasm in the throat whenever she attempted to swallow liquids, also burning and pricking along the course of the gullet, and increase of pain in these parts on pressure. There was likewise frequent vomiting of mucous and bilious matter, with burning pain in the stomach and tenderness of the epigastrium on the slightest pressure. She had farther profuse diarrhœa, with pricking pain and tenesmus. The pulsation of the heart was deep and slow, the pulse at the wrist almost imperceptible, and the breathing much retarded. In eighteen hours these symptoms continued without any material change; but the limbs were also then insensible. In twenty-three hours she died in a fit of fainting, the mind having been entire to the last.[901]—Orfila’s case was that of a gentleman who drank by mistake an alcoholic solution of corrosive sublimate, but fortunately was so much alarmed by its taste while drinking it, that he did not finish the poisonous draught. Nevertheless, he was instantly attacked with a sense of tightness in the throat and burning in the stomach, and then with vomiting and purging. Two hours after the accident Orfila found him with the face very full and red, the eyes sparkling and restless, the pupils contracted, and the lips dry and cracked. There was also acute pain along the whole 313course of the alimentary canal, particularly in the throat. The belly was swelled, and so tender that he could not bear the weight of fomentation-cloths. The pulse was 112, small and sharp; the skin intensely hot and pungent; micturition scanty, frequent, and difficult; the breathing very much oppressed; the purging bilious. The patient had likewise a tendency to doze, and was affected with occasional convulsive twitches of the face and extremities, and with constant cramps in the limbs. Next morning all the symptoms were sensibly mitigated; and they went on decreasing till convalescence was established in eight days. In the course of a few weeks he recovered his usual health, without suffering salivation.[902]—In Vautier’s case, where sixteen grains had been swallowed, the patient was immediately attacked with pain in the throat and stomach, cold extremities, trembling of the arms and legs, vomiting, paleness of the features, and great feebleness of the pulse. Vomiting being promoted by frequent draughts of warm water, and white of egg given subsequently, no further symptoms ensued, those first excited slowly subsided, and in a few days recovery took place, without any salivation. Yet it was upwards of half an hour before any measures could be taken for his relief.[903]
The only material and common symptom which was wanting in the case now related was blood in the stools and in the matter vomited. In other respects they are good examples of the ordinary train of symptoms in cases of the present variety. For other examples of the same nature the reader may refer particularly to the paper of Mr. Valentine, who has described five cases that happened at one time in the same family, the mother having attempted to poison herself and four children.[904]
It may sometimes be necessary to know the usual duration of this variety of mercurial poisoning, and also the extremes of its duration. On these points I have not hitherto had opportunities of consulting a sufficient number of cases to be able to lay down the general rule with precision. But, so far as my inquiries go, the ordinary duration in fatal cases is from twenty-four to thirty-six hours. It is probable that a few may last three days,[905] but only one instance has come under my notice where the duration was greater; and in that instance, which is described by Dr. Venables, life was prolonged under great agony from pain of the belly, bloody vomiting, diarrhœa and suppression of urine, but without salivation, for no less than eight days.[906] In cases of recovery the symptoms of irritation may continue very long, and nevertheless not pass into the second variety of this kind of poisoning,—a transition, however, which on the whole is uncommon. In the case of which an analysis has been given from Orfila’s narrative, and likewise in one of Mr. Valentine’s patients who recovered, the symptoms all along were those of irritation in the 314alimentary canal; there was not any ptyalism, or other symptom of proper mercurial erethysm.—The shortest duration yet recorded is two hours and a half. This was in a case related by Dr. Bigsby of Newark-on-Trent, where a tea-spoonful of a concentrated solution of nitrate of mercury was swallowed by a lad sixteen years old, and where the chief symptoms were burning pain from the mouth to the stomach, tenderness of the whole belly, mucous vomiting, and feculent purging.[907] In a case which occurred in London, and which has been published succinctly by Mr. Illingworth, death must have occurred either as soon, or very shortly afterwards. The dose of corrosive sublimate, though not positively ascertained, was large.[908] Next to this the shortest case recorded proved fatal in eleven hours.[909]
2. The second variety of poisoning with mercury comprehends the cases, which begin, like the former, with irritation in the alimentary canal, but in which the symptoms of what is called mercurial erethysm gradually supervene. In fatal cases of this description death sometimes arises from the primary action of the poison, exactly as in the previous variety; but in other instances it is owing to general disturbance of the constitution, or the local devastation, brought on by the secondary effects.
It is unnecessary to describe here the several forms of mercurial erethysm which may thus be developed, because they will immediately be considered under the third variety of mercurial poisoning. It is sufficient to state in passing that the leading affection is inflammation of the organs in and adjoining the mouth, and more particularly of the salivary glands.
But it may be right to endeavour in the present place to fix the period of the poisoning at which these secondary affections may and usually do commence. This cannot be done so satisfactorily as might be wished, because the cases already published which I have been able to examine do not form a large enough induction. Among the recorded cases I have hitherto seen, salivation has never been retarded beyond the third day;[910] but in an instance of suicide by corrosive sublimate which happened in the Castle of Edinburgh in 1826, and which was communicated to me by the late Dr. Shortt, the salivation did not begin till the fourth. Salivation seldom comes on sooner than the beginning of the second;[911] and the most usual date of its commencement is towards the close of the second day. There is little doubt that it may be retarded till a period considerably later than I have yet found recorded. It is doubtful whether true mercurial salivation ever begins much sooner than after the first twenty-four hours. Occasionally, however, corrosive sublimate produces salivation of a different kind, which has been mistaken for the specific variety caused by mercury. Thus in a paper on the cure of gonorrhœa 315by corrosive sublimate in single large doses, communicated by Mr. Addington of West Bromwich to Dr. Beddoes, it is stated that a grain and a half, taken at once in half an ounce of rectified spirit, causes immediately “a great burning in the throat and stomach, and quickly afterwards a copious salivation, lasting between an hour and a half and two hours, and amounting frequently to more than a quart.”[912] These facts have been appealed to by authors in medical jurisprudence as proving the rapid production of mercurial salivation. But the effect produced is not the specific ptyalism of mercury; for its brief duration is scarcely consistent with this supposition. And farther, the author goes on to observe, that, if the dose be taken on going to bed, the latter part of the night is passed quietly, and no inconvenience is felt afterwards, even when the dose is taken five or six times at intervals of three or four days. The effects here observed is a sympathetic phenomenon depending on the topical action of the poison. And such, I have no doubt, has been the nature of the salivation in several cases of poisoning with corrosive sublimate, which have been supposed to be at variance with the general rule, that this affection does not begin till about twenty-four hours have elapsed. Such seems to have been the nature of the salivation in a case published by Dr. Perry,[913] that of a girl who was attacked with swelling of the cheeks and lower lip, burning in the throat, flushed face, feeble pulse, and cold, clammy extremities after swallowing corrosive sublimate, and who had a copious flow of saliva in an hour and a half; for there is no mention made of fetor, and the girl was well enough to leave the hospital in a few days,—which could scarcely happen if she had been affected with ptyalism from the constitutional action of mercury.—In like manner Dr. Alexander Wood has related a case, fatal in fourteen days, in which the patient said salivation came on in seven hours.[914] But, notwithstanding Dr. Wood’s argument in support of the patient’s statement,—for he did not see him till nine days after the poison was taken,—there is no satisfactory evidence that the salivation was the true constitutional salivation of mercury, and not simply the result of its topical action, which seems to have been very severe.—Farther, in an instance related by Dr. H. Anderson of Belfast, where salivation appeared to him to begin in nineteen hours, it seems not improbable that he mistook for mercurial ptyalism the common salivation arising from inability to swallow on account of sore throat; for this patient too was quite convalescent in three days.[915]—Mr. Alfred Taylor alludes to a case in Guy’s Hospital of salivation occurring in four hours; but so briefly, that its true influence on the present question cannot be judged of.[916]—On the whole, then, although it is clear that ptyalism of one kind or another may occur very soon after corrosive sublimate is swallowed, it remains a matter of doubt, whether the true, specific ptyalism, depending on the constitutional 316action of the poison begins sooner than after an interval of above twenty-four hours.
As to the total duration of this variety in fatal cases, I have found an instance fatal on the fourth day, salivation having begun on the second;[917] and Orfila quotes a case from Degner, in which the gastro-enteritic symptoms were succeeded by ptyalism about the same period, and which proved fatal in fifteen days.[918] These periods, however, probably do not form the extremes; for in such cases as the former death is the consequence of the primary affection, and may therefore ensue immediately after the secondary stage has begun to develope itself; and when death arises from profuse salivation, as in Degner’s patient, or from the ravages committed by ulceration and gangrene, it may be delayed almost as long as in cases of the third variety of mercurial poisoning, in which there is no precursory stage of inflammation in the alimentary canal.
Death may arise, not only from the primary action of the poison, or from the exhaustion caused by mercurial erethysm, but likewise from incidental occurrences. Thus, in Dr. Alexander Wood’s case, referred to above, death arose directly from sudden profuse hemorrhage from the bowels, to the amount of six pounds.
The present variety of poisoning with corrosive sublimate may be concluded with the heads of an excellent example related in the Medical and Physical Journal. The patient, a stout young girl, swallowed soon after supper a drachm of corrosive sublimate dissolved in beer, and in a few minutes she was found on her knees in great torture. All the primary symptoms of this kind of poisoning were present in their most violent form,—burning in the stomach, extending towards the throat and mouth, followed in no long time by violent vomiting of a matter at first mucous, afterwards bilious and bloody; by purging of a brownish, fetid fluid; suppression of urine and much tenderness of the urethra and bladder; small, contracted, frequent pulse, anxious countenance, and considerable stupor, interrupted frequently by fits of increased pain. All these symptoms were developed in four hours. Subsequently the pain in the stomach became much easier, but that in the throat much worse. At length in the course of the second day, the teeth became loose, the gums tender, the saliva more abundant than natural; profuse ptyalism and great fetor of the breath ensued, and the patient expired towards the close of the fourth day.[919]
3. The third variety of poisoning with mercury comprehends all the forms of what is called mercurial erethysm. Without endeavouring to settle the precise meaning of this term, which is now used in rather a vague sense, I shall consider under the present head all the secondary and chronic effects of mercury. These may be caused by any of its preparations, but are most frequently seen as 317the consequence of its milder compounds, either given medicinally in frequent small doses, or applied continuously to the bodies of workmen who are exposed by their trade to its fumes.
The secondary and chronic effects of mercury are multifarious enough in reality; but if credit were given to all that has been written, and is still sometimes maintained on this subject, almost every disease in the nosology might be enumerated under the present head; for there is scarcely a disease of common occurrence, which has not been imputed by one author or another to the direct or indirect operation of mercury. The present remarks, however, will be confined as much as possible to what is well ascertained, and bears on the medical evidence of poisoning with mercury, or is important in regard to medical police. With this view, salivation and its concomitants, the most usual of the secondary effects of mercury, will first be treated of. Some observations will then be made on the shaking palsy, or mercurial tremor, which is caused in those who work with mercury. And in conclusion, a short view will be taken of the other diseases which are more indirectly induced by this poison, as well as some which have been ascribed to it on insufficient grounds. This being done, the mode of action of mercurial poisons will be resumed, and a description given of their relative effects when introduced by different channels and in different chemical forms.
Of Mercurial Salivation.—Mercurial salivation may be caused by any of the preparations of mercury, and either by a single dose or by frequently repeated small doses. It may be caused by corrosive sublimate as the secondary stage of a case which commenced with inflammation in the alimentary canal; or it may be the first sign of mercurial action, as in the medicinal mode of administering calomel and blue pill. Even in the latter case a single dose, and that not large, may be sufficient to induce ptyalism of the most violent kind. When induced by a single dose it usually commences between the beginning of the second and end of the third day, rarely within twenty-four hours. But an extraordinary case is mentioned by Dr. Bright, where five grains, put on the tongue in apoplexy and not washed over, excited in three hours most violent salivation, with such swelling of the tongue that scarifications became necessary.[920] It commences with a brassy taste and tenderness of the mouth, swelling, redness, and subsequently ulceration of the gums; peculiar fetor of the breath; and at last an augmentation is observed in the flow of the saliva, commonly accompanied with fulness around the lower jaw. These symptoms increase more or less rapidly. Sometimes they are very mild; nay, this form of the secondary effects of mercury may consist in nothing else than brassy taste, tenderness of the mouth, redness of the gums, and fetor. On the other hand, the symptoms are often very violent, the salivation being profuse, the face swelled so as to close the eyes, and almost fill up the space between the jaw and clavicles, the tongue swollen so as to threaten 318suffocation, the inside of the mouth ulcerated, nay gangrenous, and at times the gangrene extends over the face. It is not uncommon to observe severe and extensive ulceration without particular increase of the saliva.
These local affections are almost always accompanied with more or less constitutional disorder. If severe, they are attended with the symptomatic fever proper to inflammation and gangrene, from whatever cause they spring. But independently of that, mercurial salivation is accompanied, and indeed commonly preceded, by a constitutional disorder or symptomatic fever of its own, which occasionally exhibits some peculiarities. The mildest affection of the mouth and salivary glands is very generally preceded by some exaltation of the pulse and temperature, and other symptoms of fever. But when the local disorder begins violently, and above all when this takes place by idiosyncrasy from small doses of mild preparations, there is often great rapidity of the pulse, irregular action of the heart, and various nervous disorders possessing the hysteric character,—all of which, except the quick pulse, will sometimes gradually abate or even disappear, when the salivation is fairly established.
The phenomena of ordinary mercurial salivation being familiar to every practitioner, it is unnecessary to quote here any illustrative example; but the following instance may be given to exemplify its most malignant forms. A patient of Mr. Potter of Chipping-Ongar, in Essex, after taking eighteen grains of blue pill in divided doses during three days, was seized with excessive salivation and great constitutional disturbance, indicated by offensive evacuations, copious sweating, bleeding from the nose, purple spots on the skin, dilated pupils, and such severe local disease that the teeth dropped out, and he expired six days after mercurial action set in.[921]
As the phenomena of mercurial salivation have been often known to lead to important evidence and much contrariety of opinion upon trials, it will be necessary to dwell at some length on some parts of the subject.
In the first instance, then, the dose which is required to bring on salivation may be noticed. It is needless to mention the ordinary quantity required in mercurial courses. A more useful object of consideration is the departure from the ordinary rule. One of the most common and important of these deviations is excessive sensibility to the action of mercury, in consequence of which the individuals who have this idiosyncrasy may be profusely salivated by one or two small doses even of the mildest preparations. Three grains of corrosive sublimate divided into three doses have caused violent ptyalism.[922] Fifteen grains of blue pill, taken in three doses, one every night, have excited fatal salivation.[923] Nay, two grains of calomel have caused ptyalism, extensive ulceration of the throat, exfoliation of the lower jaw, and death.[924] Three drachms of mercurial ointment 319applied externally have caused violent ptyalism and death in eight days. On the other hand, it is well known that some constitutions resist the action of mercurials very obstinately, so as even sometimes to appear incapable of being salivated at all. I have more than once met with cases of the last description, where mercurial courses had been continued for three months and upwards without avail. It may be added, that, except in constitutions naturally predisposed to suffer from a few small doses, a few large doses do not appear apt to excite severe salivation, or even to cause any at all. This has been clearly shown in the course of the practice lately introduced of administering calomel in doses of a scruple. On that subject more will be said by and by. At present I may mention, that, in conformity with the practice alluded to, I have several times, in various diseases, given eight or ten grains of calomel five or six times a day for two or three days together, without observing that ptyalism was apt to ensue.
The next point to be considered is, whether mercurial salivation can be confounded with any other affection. In a very difficult case of poisoning which was tried here in 1817, that of William Patterson for murdering his wife,[925] it appeared probable that he had given her repeatedly large doses of calomel. But the proof of this was circumstantial only, and an important circumstance in the chain of evidence was a deposition to the occurrence of salivation during the woman’s illness. This fact, however, rested on the skill and testimony of a quack doctor only; and the admissibility of such a person to decide on a point of this nature, will depend on the facility with which the true mercurial form of salivation can be recognised. This statement will show the practical object of what is to follow.
Many other causes may excite a preternatural flow of saliva. Several other poisons may have that effect, for example, preparations of gold, preparations of copper, antimony, croton-oil, and foxglove: foxglove has been known to cause violent salivation for three weeks.[926] Opium too has occasionally excited salivation,[927] and also hydrocyanic acid and iodide of potassium.
Even a common sore throat, if the swelling and pain are so great as to render swallowing very difficult and distressing, may be accompanied, as every physician must have remarked, with a profuse flow of saliva; and in the ulcerative stage there is also often a fetor that is hardly distinguishable from the mercurial kind. In the ulceration of the mouth called cancrum oris there is some salivation with great fetor of the breath.
Salivation likewise forms an idiopathic disease, and may then be both profuse and obstinate. Mr. Davies has described a case of spontaneous ptyalism which had lasted for a fortnight before he was called to see the patient; and during all that time the quantity of saliva discharged was two or three pints daily. How long it endured afterwards he does not mention; but it must have continued for some time, because during his attendance first one physician and 320then another were called into consultation with him. Laxatives slowly removed it. Mr. Davies has not described the state of the mouth; but the first physician mistook the salivation for a mercurial one.[928] In the same journal which contains this case another has been related which lasted four months.[929] Another very remarkable case has been recorded by Mr. Power. The patient, a young lady, discharged for more than two years from sixteen to forty ounces of saliva daily. In the last two cases the mouth was not affected.[930] Two other instances have been related by M. Bayle, in one of which the patient was cured after spitting five pounds daily for nine years and a half; while the other continued to be affected after spitting profusely for three years. In neither was there any ulceration of the mouth.[931] An instance has been related by an Italian physician, Dr. Petrunti, where, in the course of various nervous affections of the hysteric character, the patient became affected with heat and tightness in the throat, and so profuse a salivation for two months, that between three and four pounds were discharged daily.[932] A case somewhat similar is related in Rust’s Magazin of a man who suffered upwards of two years from a daily salivation alternating occasionally with a mucous discharge from the bowels or lungs.[933] M. Guibourt describes the case of a lady who had an attack of profuse salivation every thirty, forty, or fifty days, lasting between twenty-four and forty-eight hours, and unaccompanied with any other affection of the mouth or adjoining parts except a sense of tightness in the throat.[934] M. Gorham relates an interesting case of a lady who in three successive pregnancies was attacked soon after impregnation with excessive ptyalism, which continued to the extent of between two and four quarts daily until the period of quickening on two occasions, and on the third till her delivery; but there was never any fetor or any affection of the gums.[935] I have likewise met with a singular case where spontaneous ptyalism accompanied an ulcerated sore throat of the mercurio-syphilitic kind. The patient had taken mercury to salivation about six months before coming under my care, and got completely rid of both the sore throat and salivation. But the sore throat returned, together with the salivation, two months before I saw him, and the salivation continued for two months longer to the extent of twenty or even thirty ounces daily,—the ulcer of the throat during that interval being sometimes healed up, and again returning as severely as ever. In three weeks more the discharge rapidly diminished, and ceased. During all the time he was under my care there was no fetor of the breath, and no redness, ulceration, or sponginess of the gums. A singular account of an epidemic salivation which occurred in connection with a continued tertian fever, 321has been given in an inaugural dissertation contained in one of Haller’s Collections. The author, Quelmalz, says that the ptyalism sometimes continued for three weeks, that it was in one instance as great in extent as the most violent mercurial salivation, and that it was accompanied by fetor, superficial ulceration of the mouth, pustules on the tongue, relaxation of the gums, and looseness of the teeth.[936]
Salivation may likewise be produced by the influence of the imagination. I have seen a singular example of this. A woman who had a great aversion to calomel was taking it with digitalis for a dropsical complaint. Some one having told her what she was using, she immediately began to complain of soreness of the mouth, salivated profusely, and even put on the expression of countenance of a salivating person, although she had taken only two grains. On being persuaded, however, that she had been misinformed, the discharge ceased gradually in the course of one night. Two days afterwards she was again told on good authority that calomel was contained in her medicines, upon which the salivation began again and was profuse. It did not last above twenty-four hours; but the symptoms during that period resembled a commencing mercurial salivation in every thing but the want of fetor and redness of the gums.
In general, mercurial salivation may be easily distinguished from all the preceding varieties by an experienced practitioner. If its progress has been traced from the first appearance of brassy taste and fetor to the formation of ulcers and supervention of ptyalism, no attentive person can run any risk of mistaking it. Its characters are also quite distinct at the time salivation just begins. The fetor of the breath and sponginess and ulceration of the gums at this stage distinguish it from every other affection. But if the state of the mouth is not examined till the ulcers have existed several days, the characters of the mercurial disorder are much more equivocal. They cannot be distinguished, for example, from some forms of idiopathic ulceration of the mouth connected with unsoundness of the constitution, and characterized by extensive sloughing, ptyalism, and gangrenous fetor.[937] In particular they cannot be distinguished from the effects of the disease called cancrum oris. A few years ago indeed a London physician was charged, in consequence of this resemblance, with having killed, by mercurial salivation, a patient to whom it was proved that he had not given a particle of mercury, and who clearly died of the disease in question;[938] and a similar case, where fatal mercurial salivation was suspected, but which was clearly proved on a Coroner’s Inquest to have been also a case of cancrum oris, has been more lately published by Mr. Dunn.[939]
For distinguishing these and such other affections from mercurial 322salivation Dr. Davidson of Glasgow has lately proposed a character, the exact scope of which cannot yet be appreciated,—namely, that in true mercurial salivation there is never any sulpho-cyanic acid in the saliva; so that sesquichloride of iron does not render it red. The presence of sulpho-cyanic acid may possibly prove that salivation is not mercurial; but the converse does not hold good, because other causes tend to deprive human saliva of its sulpho-cyanic acid.[940]
The next point to be noticed regarding mercurial salivation is, that a long interval may elapse after the administration of the mercury has been abandoned, before the effect on the salivary glands and mouth begins,—mercury in small doses being what is called a cumulative poison, or a poison whose influence accumulates silently for some time in the body before its symptoms break forth. Swédiaur has met with instances where the interval was several months,[941] Cullerier with a case in which it was three months.[942] It will at once be seen how strongly such facts may bear on the evidence in a criminal case, where the administration of mercury in medicinal doses, which have been long abandoned, is brought forward to account for salivation, appearing weeks or months after, and giving rise, in conjunction with other circumstances, to a suspicion of mercurial poisoning of more recent date.