Antiseptics are drugs which arrest putrefaction, either by-preventing the growth of, or completely destroying the microorganism on which decomposition depends. Some authors limit the use of the word to those drugs which restrain the development of micro-organisms, and call those substances which destroy the vitality of micro-organisms, germicides or disinfectants. The term disinfectant, by extension, is applied to those agents which kill non-pathogenic bacteria as well as to those which destroy disease germs.

Statements are most discordant as to whether certain substances are antiseptics, and as to the strength of their antiseptic power. This is because antiseptics act differently on different organisms; and the distinction has not been drawn between preventing the growth of, and destroying micro-organisms. Also because the power of antiseptics depends upon the temperature at which they act, the medium in which they are dissolved, the strength of the solution, the time given them to act, and the number of micro-organisms present in the substances to which they are added.

To properly test the value of an antiseptic the above conditions must be noted. All instruments and substances - except the fluid containing the micro-organisms to be tested - are heated so that any adventitious micro-organisms are destroyed. A cultivating medium, such as agar-agar jelly, in which the micro organisms will grow, is selected, and two test-tubes, each containing some of it, are taken; to one of these the supposed antiseptic is added. Some fluid containing the micro-organisms is then added to both test-tubes; both are plugged with sterilized cotton to prevent the entrance of germs from the air, and it is observed whether the micro-organisms will grow in the tube containing no antiseptic, but not in that containing the antiseptic. As the power of an antiseptic depends on so many circumstances, no exact order of their potency can be given, but roughly the more powerful are placed first in the following list; the last are very feeble.

1. Heat. - This is the best antiseptic, but a temperature of at least 212o F. 100° C. is required. After an infectious fever, clothing, bedding, etc., may be heated in a dry-air chamber to between 200° and 300° F. 93.5° and 149° C; or what is far better, as dry air does not penetrate the spores nearly so well as moist, and the interior of the rolls of fabrics often hardly gets heated at all, steam under pressure may be driven through them. Another useful way is to boil the infected things in water. Surgical instruments are disinfected in this way but one per cent. of washing soda (sodium carbonate) should be added to the water to prevent their rusting.

2. Corrosive Mercuric Chloride. - A solution of 1 in 1000 is constantly used for washing hands, and for many other purposes connected with midwifery and surgical operations. For most uses one part to 3 or 5000 of water or even weaker, is the limit of safety. Gauze of the strength of I to 2000 will blister, if the skin is damp.

3. Formaldehyde, of which the forty per cent. solution is known as Formalin, has extraordinary power as a surface disinfectant, greater than that of any known substance. It is especially useful for the disinfection of rooms and their contents when volatilized from a specially constructed lamp.

4. Chlorine is, as a rule, too irritating. Chlorine gas, disengaged by the action of hydrochloric acid on manganese dioxide, may be used to disinfect a room, the windows, chimneys and doors of which are sealed. It must be remembered that it attacks and bleaches many substances.

5. Chlorinated Lime is the best antiseptic for all excreta (Sternberg).

6. Bromine, and, 7, Iodine are rarely used, as they are too irritating.

8. Carbolic acid is used but infrequently. If surgical instruments have been previously sterilized, the use of carbolic acid indicates a distrust, on the part of the surgeon, of his assistants.

9. Quinine, and, 10, Salicylic acid are too expensive for ordinary use.

11. Iodoform is commonly used to dust upon wounds, etc.

12. Boric acid is used for many surgical purposes.

13. Zinc chloride, and, 14, Potassium permanganate, are much used domestically.

15. Solution of Hydrogen dioxide is the ingredient of various popular disinfectants.

16. Oleum Eucalypti is used in surgery.

17. Sulphurous acid, disengaged by the burning of sulphur, is used to disinfect rooms.

18. Creosote, 19. Benzoin, 20. Zinc sulphate, 21. Ferric oxide, 22. Thymol, 23. Alcohol, 24. Balsam of Tolu, 25. Balsam of Peru, are none of them much used.

26. Lysol, Creolin and various cresol compounds are not pharmacopoeial, but they are powerful and much employed.

We do not know of any drugs which, when taken internally or inhaled, will certainly destroy micro-organisms, either in the gastro-intestinal tract or respiratory passages, unless they are sufficiently concentrated to be fatal to the patient. Some authorities, however, consider that naphtol, calomel, and some other substances will destroy many varieties of micro-organisms in the stomach and intestines. The fact is often lost sight of that an infinitely small amount of a remedy which could not be administered in sufficient amounts to destroy, will often completely inhibit the growth of micro-organisms, and thus should be classed as an antiseptic

Deodorants, or deodorizers, are substances which destroy disagreeable smells. There are too many for enumeration. Many antiseptics are deodorizers. Charcoal is often called a disinfectant, but it is merely a deodorizer; it is powerless if it is wet.