The most convenient antiseptic for general use is _Carbolic Acid_. This is a clear, colourless liquid of rather oily consistence, which rapidly becomes converted into solid crystals in cold weather. When required for purposes of disinfection it should be mixed with 39 times its quantity of water, or roughly one pint of water requires one tablespoonful of pure Carbolic Acid to make a solution of 1 in 40. This solution is required for soaking the hands after they have been washed with soap and warm water, and the nails scrubbed with a nail brush. This latter proceeding is one of _ordinary cleanliness_, the soaking in the Carbolic Acid solution, which should be warm, is in order to obtain _Surgical Cleanliness_. It will be readily understood, that if the hands come in contact with any possible source of infection after this soaking, then it must be repeated before beginning the operation. The disinfection of the hands must be the last stage in all the preparations for the circumcision. A similar solution of 1 in 40 Carbolic Acid may be used for placing the instruments in before the operation. They are to be taken directly out of the solution as required. A shallow dish of a material easily cleaned, as metal, glass or porcelain should be filled with 2½ ounces (5 tablespoons) of water which has been boiled, and to this one half a teaspoonful of Carbolic Acid is added, taking care that the acid is thoroughly well mixed up with the water and not allowed to float about in droplets. If the instruments are scrupulously clean, i.e., if they have been washed thoroughly with soap and hot water, they require to remain for _one hour_ in the Carbolic Acid solution to render them sufficiently disinfected for operating purposes. It is therefore quicker, as it is also more scientific, to _sterilize the instruments before using them_. By sterilizing them we kill any micro-organisms that may be present on them, and we are then confident that no living germs are carried to the wound by means of the instruments. In other words they are _aseptic_. Instruments are sterilized by boiling for about ten minutes in clean water. It is useful to add washing soda in the proportion of 5 grains to every two tablespoons of water. It is obvious that the instruments must be of metal, as no other material will stand boiling. They must be made in such a way as to prevent the accumulation of dust or dirt in joints or crevices.