Small (therapeutical) doses of any preparation are usually well borne by the stomach. Rabuteau cites cases where many hundred pilules of proto-iodide have been taken in the course of one to three years without any gastric disturbance: yet we must allow for some idiosyncrasy in this respect, and practically we find that those who have resided long in the tropics, and fair, delicate women and chronic dyspeptics are very sensitive. It is not, however, possible to say beforehand what amount of mercury will produce the characteristic effects on any given case - a single friction or a few grains may produce in one patient what many weeks of treatment will not do in another. Single doses of calomel - from 1 to 5,10, or even more grains - produce thin and "bilious" stools without much griping. If the intestine of an animal be examined after such actions, it will be found reddened, especially in the upper part, and its glands stimulated. As a rule, ordinary care will early detect symptoms of constitutional action in the mouth, such as a sense of heat, metallic taste, sticky coating of the tongue, increased flow of saliva, and perhaps slight tenderness of the gums. On continuance of the medicine, these latter symptoms increase and diarrhoea occurs, with some nausea. The stools, at first feculent, become thin and sometimes papescent with mucus, sometimes yellow, or dark or grass-green (the latter especially in children: they have been compared to "chopped spinach"): sometimes blood appears in the motions, and severe colic and tenesmus occur. The tongue is said to show a greenish coating with two longitudinal red stripes (Traube). In severe cases, when the poisonous action of mercury has been induced, intense stomatitis appears, with swelling of the tongue and gums, membranous deposit, fetor, loosening of teeth, and severe pain and difficulty in mastication. The salivary glands become enlarged and tender, and a vast amount of secretion pours from the mouth: 10 lbs. of it have been secreted in twenty-four hours: at first viscid as usual, it soon becomes thin and very watery, containing albumen, mucus, and alkaline chloride (Thompson). Children and the aged are seldom salivated- Graves suggests because their salivary glands are "inapt" - diarrhoea or prostration is with them the earliest symptom. Salivation is connected, too, with local causes: it comes on more quickly when the mouth is unclean, and may be almost wholly prevented by great care with the teeth: dental caries will determine it; it is said to commence by the last molar of the side on which the patient mostly sleeps (Ricord): also the irritation of a wisdom-tooth, or of a pipe, will influence it.

Such facts have led to the supposition that salivation is only secondary to buccal soreness, but this is incorrect: it may be induced by rubbing mercury over the parotid, and before any irritation is produced. Ricordi detected the drug in saliva drawn from Steno's duct, by a catheter, in animals, when calomel had been injected beneath the skin; and salivation occurs, as we know, independently of mouth-irritation from the action, e.g., of gold, iodine, various acids, etc., as well as during pregnancy and certain diseases. The safe test of a mercurial salivation is detection of the metal in the secretion. Women seem to be more readily affected in this way than men, and the subjects of granular kidney, of scrofula, and of scorbutus are peculiary susceptible (Christison and others). It occurs more frequently under fractional (non-purgative) doses of calomel, or inunction of blue ointment, than from fumigation, suppositories, or injections: it is markedly less under the use of sublimate, iodide, or cyanide, than of insoluble preparations, either on account of the smaller dose of the former employed, or of some peculiarity in their elimination. Ulceration, or sloughing of the gums, hemorrhage, periostitis, and prostration of even fatal character have occasionally followed a profuse salivation, and necrosis, scars, and contractions have accompanied even recovery.

We have seen that a local action, irritant in character, is exerted by most compounds of mercury on the alimentary tract; but H. Wood speaks of calomel as "free from all irritant properties," and Lente argues that large doses (one teaspoonful) act in a sedative manner (New York Journal, 1870, vol. xi.) - this was the argument of Annesley, but it is not a safe one to act upon. The irritation excited by corrosive sublimate in toxic doses is, however, the most severe: there is an acrid taste, and a sense of burning and constriction in the mouth and fauces, with whitening: and shrivelling of mucous membrane if the dose be concentrated: vomiting and purging with tenesmus usually occur, with passage of blood, suppression of urine, and general symptoms of gastro-enteritis: after death, signs of inflammation, contraction, or ulceration have been found, especially in the stomach and upper part of the intestine, and that this is not merely a local effect is proved by its occurrence when the drug has been administered by the skin. Profound depression is usually a symptom of sublimate poisoning, and is sometimes more marked than pain, vomiting, or purging; salivation is by no means constant in acute cases.

The iodides of mercury act much like corrosive sublimate, the red iodide being more actively irritant than the green one. The red oxide produces similar lesions of the intestinal canal (Orfila); it is not given internally in medical practice, nor is the ammonio-chloride (white precipitate), but in a case when a large quantity of the latter compound caused death, the stomach was found contracted, and its lining membrane ecchy-mosed (Guy's Reports, 1874). The liquor hydrargyri nitratis has produced intensely severe effects on the intestinal tract, and irritant poisoning has followed the accidental use of the sulphides and the cyanide of mercury.