These symptoms appear in adults, generally with great regularity, when a similar quantity of mercury has been taken in a similar time, though the effect is modified by various conditions, as age, sex, the presence of disease, etc.

When persons are exposed for a long time to the fumes of mercury, and the metal is thus taken in in very small quantities for a lengthened period, a different effect is sometimes produced. This is called mercurial cachexia. In this condition the appetite is lost, the gums become livid and bleed easily, the breath is foetid, the tonsils and fauces become congested or even ulcerated, and a tendency to diarrhoea is often present. In bad cases vomiting and purging generally occur.

The lips become pale, the complexion earthy, the person becomes emaciated, the hair sometimes falls out, the muscles become weak and small. The person is easily affected by changes of weather; there is a tendency to fainting, uneasiness, and anxiety; the pulse and respiration become quick; the pulse is also small and intermittent; and palpitation becomes very troublesome. The intellect is dull, and rheumatic pains are felt in the muscles of the extremities, more rarely in those of the trunk.

These symptoms go on increasing, and new ones also appear. Mercurial tremors occur in the muscles, beginning generally in the upper extremities, and gradually extending till the patient cannot execute any movement, and the speech itself becomes stammering.

Mercurial paralysis of muscles or groups of muscles occasionally occurs. Generally this is confined to the muscles of the upper extremities, but sometimes affects other muscles, such as those of the larynx, causing mercurial aphonia. These paralyses generally occur in the later stages of mercurial erethism, and rarely occur before the other symptoms.

The mental qualities become also affected. Ill-humour, irritability, melancholy, and fear of death occur in some persons, and in others, though very rarely, idiocy, and still more rarely, furious mania. In some instances epilepsy has been observed.

Mercury in the form of organic compounds appears to have a special action on the brain. The symptoms are those of impairment of the special senses, sight, taste, hearing, of motor power, and of the cerebral functions. Two chemists who were engaged in the preparation of mercuric methide during three months, suffered from weakness and dimness of vision, and one of them from some soreness of the gums, nausea, and vomiting. At the end of this time the symptoms became much worse, deafness and numbness came on, and were succeeded by a semi-comatose condition with great restlessness. In the one who had not previously suffered from soreness of the gums, this now appeared, along with foetor of the breath; the urine was albuminous, Cheyne-Stokes' breathing was observed, the evacuations were passed involuntarily, and he died comatose a fortnight after the symptoms became severe. Sensibility was retained nearly to the last. In the other patient, impaired sensation, loss of power to direct movement, and muscular feebleness were succeeded by involuntary passage of evacuations, an idiotic condition of restlessness, and violent muscular movements, especially when he was touched. After remaining in an idiotic state for a year he died of pneumonia.

The action of mercury may be modified by sex, age, or idiosyncrasy. Women, as a rule, are more easily affected than men, whilst children may take mercury in considerable quantities without showing any symptom of salivation. In certain persons large quantities of mercury may be administered for a length of time without producing much more effect than in children, but in others exceedingly injurious results may follow very minute doses. A case of salivation from as little as a grain and a half of calomel has been recorded, and from one-eightieth of a grain of corrosive sublimate. In typhus it is very hard to produce salivation, but in persons suffering from Bright's disease, although mercury may be useful as a purgative, it requires to be given with caution, on account of the violent effects which may follow even small doses.

Mercury combines with albumen, and forms albuminate of mercury, which is insoluble in water, but is easily soluble in excess of albumen or in chloride of sodium. This compound may be formed in the stomach or intestines, and a compound of mercuric oxide with albumen is probably the form under which mercury, however administered, circulates in the blood. When taken into the stomach, mercuric salts are powerful irritants, and, when given in large quantities, cause gastro-enteritis, vomiting, and purging, with bloody stools. Finely divided metallic mercury and mercurous salts are less irritating, and act simply as purgatives.

A good deal of discussion has arisen regarding the action of mercury on the liver. It has long been ranked as a cholagogue, and there can be no question whatever that mercury and its compounds are very beneficial in cases of so-called bilious disorder characterised by feelings of laziness and apathy, inability to think, dislike of exertion, not unfrequently combined with irritability of temper, deranged digestion, and slight yellowish tinge of the eyes. When bile was supposed to be formed in the blood, and to be only excreted by the liver, the beneficial effect of mercury was attributed to a stimulating action on the liver, whereby it increased the rapidity of the secretion, and thus removed the bile more quickly from the blood. But it was found on experiment by Dr. Scott that mercury does not increase the rapidity of the biliary secretion, and this result was confirmed by a committee of the British Medical Association, the chief members of which were Hughes Bennett, Rutherford, and Gamgee, and also by later experiments made by Rutherford, Vignal, and Dodds. As we now know that bile is formed by the liver, and not merely separated from it by the blood, we can understand that the real action of mercury as a cholagogue consists, not in its stimulating the liver to form more bile, but in removing more readily from the body the bile which is already present in excess. It appears to perform this function by stimulating the upper part of the small intestine, and thus causing the evacuation of the bile before time has been allowed for its reabsorption. For the liver does not merely form bile, it also excretes bile which has been previously formed and reabsorbed from the intestine. The bile may thus serve several times over. It is formed, passes from the liver into the duodenum, is reabsorbed, and carried by the portal blood to the liver, where it is again excreted and poured out through the bile-duct a second time (p. 404). Part of it, however, is carried down the intestine, decomposed, and evacuated, and to supply the place of this a certain amount of new bile is constantly being formed, which is poured into the intestine along with the old. It is evident that any drug which acts upon the lower part of the intestine will have little power to remove the bile, as this will have undergone absorption already in the upper part of the digestive tract. But any drug acting upon the duodenum will cause the bile to be rapidly moved on and its absorption to be prevented. More especially will this be the case if the cholagogue be combined with a saline purgative, which, by causing a profuse secretion of watery fluid, will wash the bile out. This action on the upper part of the small intestine is probably possessed by mercury, and the reasons for this supposition are : (1) that it is so beneficial in bilious disorders; (2) that it does cause the appearance of bile in the stools, for Buchheim has found by analysis that the green stools which occur after purgation by calomel actually owe their colour to bile; and (3) that in the stools passed after mercurial purgatives, leucin and tyrosin, the products of pancreatic digestion, have been found, showing the rapid peristalsis produced. Mercury acts as a disinfectant of the intestinal contents.

After the absorption of mercury into the blood, it is said, in small doses, to increase the number of blood-corpuscles; in larger doses, however, it produces anaemia, but how far these results are dependent upon the improvement or disturbance of the digestion, and how far upon the action of the mercury itself upon the blood, has not been ascertained. Albuminate of mercury, when added to blood out of the body, gradually destroys the corpuscles.

Mercury appears to have the power of causing absorption of fibrinous exudations, for the fibrinous adhesions observed in syphilitic iritis have been seen to disappear as the patient was brought under the influence of mercury. When mercury is used for a long time, it appears to lessen greatly the force of the pulse, and large doses of mercuric preparations, when brought into contact with a frog's heart, will arrest its pulsations immediately.

The respiration is affected in persons who have been taking too much mercury, and becomes laboured and accompanied by a feeling of constriction. The temperature is rarely affected, excepting secondarily, in consequence of local inflammations which the mercury may excite, although sometimes mercurial fever (p. 682) precedes any marked local change.

Mercury is excreted by the saliva, bile, urine, sweat, and milk. The salivation which it produces is probably due in part to reflex excitement of the salivary glands by the irritation of the tongue, but it is no doubt also in part due to irritation of the nerves of the gland, or of the gland-structure itself, by the mercury. The urine is said to be somewhat increased, and it is stated that the addition of a little mercury to digitalis and squill greatly increases the diuretic action of these drugs. Calomel has an undoubted diuretic action, and it has been suggested that it owes this action to the increase of urea in the blood, produced by part of the salt being changed into mercuric chloride, which acts as an hepatic stimulant (cf. p. 432).