Antiseptics (Gr. against, and putrid), substances or means which prevent or arrest putrefaction. Putrefaction is a process which highly complex organic bodies undergo when subjected to the proper conditions of heat, moisture, and air, and no longer controlled by the laws of vital chemistry. Nitrogenous or albuminoid bodies are essential to this process, in which they play the double part of being themselves decomposed and, by an imperfectly understood action called catalysis, exciting allied changes in other bodies. The growth of living infusorial organisms holding a very low position in the scale of animal or vegetable life, called vibrios and bacteria, is a frequent if not invariable accompaniment of this process; but it is still a question how essential they are in its production. The methods of preventing organic decomposition depend upon the removal of some one or more of the conditions necessary for its accomplishment. The temperature may be above or below the limits at which putrefaction can go on. The preservative effect of cold, and especially of dry cold, is well known, and exemplified in the keeping of meat and fruit on ice or in ice houses.

Animals have been found undecomposed in the ice of Siberia, which belong to extinct species and which must have been embalmed in ice for age3. A boiling temperature coagulates albumen, kills infusorial organisms, and temporarily arrests putrefaction, until the material receives a new ferment from without. The exclusion of air, as in the process of canning fruit and meat, renders the result more permanent. Many substances withdraw water from the tissues, and also from the infusorial organisms, thus causing them to shrivel up and lose their activity. Such are sugar, glycerine, alcohol, and many salts, as common salt, saltpetre (nitrate of potassa), and alum. Fruits are largely preserved in sugar; many medicinal fluid extracts may be made with glycerine; and anatomical specimens may be preserved almost indefinitely in glyeerine or alcohol. Salt and saltpetre are of the highest value in the preservation of meat. If the water is simply driven off by the heat of the sun and atmosphere, meat may be kept unchanged for a long time in a dry climate Several of the agencies first mentioned, such as boiling water, alcohol, and some salts, as well as corrosive sublimate, chloride of zinc (Burnett's disinfecting fluid), and tannin, act by coagulating and rendering chemically inert albuminous substances.

Corrosive sublimate is used but little except for anatomical purposes. Chloride of zinc is an excellent disinfectant for ships, hospitals, dissecting rooms, and water closets, and is also used to preserve bodies for dissection. Tannin forms with the gelatine of the skin, in leather, one of the most enduring of organic compounds. Prof. Brunetti of Padua has used tannic acid very successfully in the preservation, as anatomical specimens, of various internal organs. Bodies have been found perfectly preserved in peat bogs, that must have been undergoing the tanning process for hundreds of years. Many of the most useful antiseptics act not only in one or more of the ways mentioned, but also either as poisons to the infusoria accompanying decomposition, or as opposing the catalytic action of ferments. Quinia, for instance, has been found to have both these properties in a high degree, killing infusoria immediately in the proportion of one part to 800, in some minutes at 1 to 2,000, in some hours at 1 to 20,000, and preventing or retarding the formation of carbonic acid from sugar, the reaction of emulsine upon amygdaline, and of ozone upon guaiacum. As a preservative against actual putrefaction, it was found, weight for weight, less efficient than corrosive sublimate.

Carbolic acid, creasote, chloroform, and perhaps the volatile oils, act in this way. Carbolic acid has been largely used of late years as a surgical antiseptic dressing, in watery solution, 1 to 30; diluted with glycerine, with alcohol, with oil, as putty, or as plaster with shellac. The antiseptic treatment demands that all wounds should be carefully protected from the air by some of the forms of carbolic acid dressing just mentioned, even a finger used in examination or an amputating knife being dipped in carbolic acid oil, lest they should carry living germs to the wounded sur-face. The action of creasote finds useful application in the smoking of meat. Volatile oils and resins were probably the active agents in the ancient process of embalming. Chlorine, and sometimes iodine, act as disinfectants by withdrawing hydrogen from products of putrefaction, allowing the nascent oxygen and other remaining elements to form simpler and more stable combinations, and as antiseptics by poisoning infusoria or destroying the activity of ferments.