+AGENTS EMPLOYED TO SECURE ASEPSIS+ +Bichloride of Mercury+ is used for the disinfection of the hands and skin and for the irrigation of wounds. Biniodid of mercury is extensively employed and in the same strengths as the bichloride. It is, however, a more powerful germicide, while being less irritative, and neither forms a mercuric albuminate nor tarnishes metal instruments. +Carbolic Acid.+ This acid is derived from coal tar, and although known as early as 1834 as the first antiseptic recommended and used by Lister, is not so popular since the discovery that bichloride of mercury possesses more germicidal action. Gangrene of the skin and subjacent tissues has often been traced to the long continued use of dilute solutions of carbolic acid or of ointments containing small quantities of the drug. Gangrene of the fingers and toes is by no means infrequent as a consequence of its use. Another condition frequently seen is the systemic poisoning through absorption. One of the first symptoms noticed from such absorption is irritation of the urinary tract and carboluria. This poisoning is more apt to take place when the weaker solutions are used than when the pure acid is used, as the destruction produced by the pure acid prevents its absorption. The effect of carbolic acid upon the urine (See Chapter II, “_Carbolic Acid_”) is to cause it to become smoky a short time after it is voided. The urine shows a complete absence or diminution of the sulphates, and albumin is generally present. When these symptoms present themselves, the use of carbolic acid should be withdrawn, and the administration of sulphate of soda and atropin begun. If the condition has existed for any length of time and the patient is weak and exhausted, stimulants are indicated. +Lysol+ is a saponified phenol, and possesses some germicidal power. It is used in strengths of 1 to 3 per cent. solutions. +Creolin+ is mildly germicidal and is used a great deal in from 2 to 4 per cent. solutions. Both lysol and creolin act very much like carbolic acid, but neither possess its irritating qualities. +Formaldehyde Gas+ is an active germicide and very valuable as a disinfectant. It is used in the shape of formalin which is a 4 per cent. solution of the gas in water. This agent is very irritating to the normal tissues in the stronger solution, but a 2 per cent. solution of formalin may be used for the sterilization of the hands, instruments, etc. The formaldehyde fumes are employed for the disinfection of clothing, rooms, bedding, and also for the sterilization of catheters. The fumes of the gas are very irritating to the mucous membrane and when this agent is used for the disinfection of rooms, every crevice and crack must be tightly sealed to prevent the escape of the gas.