External

Corrosive mercuric chloride is one of the most powerful and important antiseptics with which we are acquainted. In 1870 it was discovered that 1 part in 6000 would kill infusoria and spermatozoa. Now it is known to be a universal germicide. The published results of experiments with it vary very much, because the duration of the action, the solvent, and the micro-organism experimented upon, are not always the same. Evans found that anthrax spores were destroyed by corrosive mercuric chloride solutions of 1 in 1000 acting for a quarter of an hour, and 1 in 3000 acting for one hour. The bacilli themselves were destroyed by solutions of 1 in 15,000 acting for one minute, and 1 in 25,000 acting for half an hour. A solution of 1 in 70,000 prevented the growth of the spores, and one of 1 in 500,000 prevented the growth of the bacilli. A reference to carbolic acid will show how much more powerful corrosive mercuric chloride is. A. solution of 1 in 1000 is very commonly employed for many disinfecting purposes. If albumin be present in the fluid to be disinfected, an albuminate of mercury is formed, and the antiseptic value of the fluid is destroyed. This change may be prevented by the addition of 5 parts of either hydrochloric, citric or tartaric acid to 1 of corrosive mercuric chloride. The red mercuric iodide is also a powerful antiseptic. Metallic instruments cannot be disinfected with the corrosive chloride for mercury deposited on them.

Most mercurials, especially the oleate, oxide, ammoniate, nitrate and corrosive chloride, will destroy the animal and vegetable parasites that infest the skin; they are, therefore, anti-parasitic. Also, most of them will occasionally relieve itching, even when no cause is to be found.

The mercurial preparations, especially the red mercuric iodide and the acid solution of the nitrate, are powerful irritants. The latter is strongly caustic. Mercurous salts are slightly irritant and stimulating; calomel is sometimes applied to sores for this property.

Metallic mercury and its salts are absorbed by the skin, especially when rubbed in either as an oleate or an ointment. These preparations are also taken up, although to a less degree, if simply applied to the skin, for minute particles of mercury or its salts pass into the hair follicles and sebaceous follicles, from which they are absorbed as an oxide or a chloride. All the symptoms of mercurial poisoning can be produced if the drug is absorbed through the skin. The vapor can be absorbed through the mucous membrane of the lungs, and mercury compounds are so volatile that when they are applied to the skin some usually enter the blood by the lungs.

Internal

Although the different salts of mercury have different external actions, after absorption their actions are, in most respects, similar. The long-continued use of excessive doses of mercurials produces well-marked and important symptoms {see Toxicology). The actions for which mercurials are used in medicine are the following:

Stomach And Intestines

The metal mercury itself and mercurous compounds, being mildly irritant in their action, are often used as purgatives; but the mercuric compounds given in the same doses produce severe gastro-intestinal irritation. The action is chiefly on the duodenum and upper part of the jejunum; the precise mode of irritation is unknown, but it is certain that, in consequence of the administration of the mercurial, the contents of the duodenum are hurried along before there is time for the bile to be reabsorbed, and hence the motions are very dark-colored. There is probably some, but not an excessively increased secretion from the intestinal walls, for the motions, although large and loose, are not watery. As the action of the mercurial is chiefly on the upper part of the intestine, it is greatly assisted by giving a saline purge a few hours after it, for this will act more on the lower part of the bowel. The contents are passed along so quickly, that it is doubtful whether there is time for much mercury to be absorbed if a purgative dose of it has been given. Calomel and the metallic preparations are the two forms most used as purgatives. The former is the more powerful.

Whatever compound of mercury is taken by the mouth, it, in the stomach, becomes a complex albuminate containing mercury, sodium, chlorine, and albumin. This compound, in the presence of the sodium chloride in the stomach, can exist in solution there. Precisely what happens to it in the duodenum is doubtful; but it is quite certain that if the dose is insufficient to cause purgation some mercury is absorbed, the rest passing out of the bowel as a sulphide.

Liver

It was formerly taught that calomel increased the amount of bile formed by the liver. This is now known to be an error, but corrosive mercuric chloride increases it, and possibly, occasionally when calomel is administered, some of it is converted into the corrosive chloride. Large doses of calomel are said to slightly diminish the secretion of bile. Calomel and, to a less extent, preparations of metallic mercury are, however, called indirect cholagogues, because they, in the manner already explained, aid the excretion of bile. The stools are spinach- green and contain calomel, mercuric sulphide, and unaltered bile.

Blood

After absorption the mercurial compound formed in the stomach and intestines probably becomes oxidized, and circulates as an oxyalbuminate. Minute, long-continued doses of mercury slightly increase the richness of the blood in red corpuscles, and in animals may add a little to the weight of the body. Large doses produce anaemia. Mercury checks the emigration of white corpuscles, and this perhaps explains its antiphlogistic action.

Remote Effects

Mercury is excreted by the saliva, bile, urine, sweat, faeces, and milk. In small doses no effects can be attributed to this, but in large doses mercury irritates the salivary glands and is a powerful sialogogue. By itself it is a feeble diuretic, but it sometimes powerfully aids other diuretics. It is eliminated very slowly, and hence accumulates in the body.