Fishing-gut and silver wire, as well as the needles, should be boiled along with the instruments.  Horse-hair and fishing-gut may be sterilised by prolonged immersion in 1 in 20 carbolic, or in the iodine solutions employed to sterilise catgut.

The field of operation is surrounded by sterilised towels, clipped to the edges of the wound, and securely fixed in position so that no contamination may take place from the surroundings.

The surgeon and his assistants, including the anaesthetist, wear overalls sterilised by steam.  To avoid the risk of infection from dust, scurf, or drops of perspiration falling from the head, the surgeon and his assistants may wear sterilised cotton caps.  To obviate the risk of infection taking place by drops of saliva projected from the mouth in talking or coughing in the vicinity of a wound, a simple mask may be worn.

The risk of infection from the air is now known to be very small, so long as there is no excess of floating dust.  All sweeping, dusting, and disturbing of curtains, blinds, or furniture must therefore be avoided before or during an operation.

It has been shown that the presence of spectators increases the number of organisms in the atmosphere.  In teaching clinics, therefore, the risk from air infection is greater than in private practice.

To facilitate primary union, all haemorrhage should be arrested, and the accumulation of fluid in the wound prevented.  When much oozing is anticipated, a glass or rubber drainage-tube is inserted through a small opening specially made for the purpose.  In aseptic wounds the tube may be removed in from twenty-four to forty-eight hours, and where it is important to avoid a scar, the opening should be closed with a Michel’s clip; in infected wounds the tube must remain as long as the discharge continues.

The fascia and skin should be brought into accurate apposition by sutures.  If any cavity exists in the deeper part of the wound it should be obliterated by buried sutures, or by so adjusting the dressing as to bring its walls into apposition.

If these precautions have been successful, the wound will heal under the original dressing, which need not be interfered with for from seven to ten days, according to the nature of the case.

#Dressings.#—­Gauze, sterilised by heat, is almost universally employed for the dressing of wounds. Double cyanide gauze may be used in such regions as the neck, axilla, or groin, where complete sterilisation of the skin is difficult to attain, and where it is desirable to leave the dressing undisturbed for ten days or more. Iodoform or bismuth gauze is of special value for the packing of wounds treated by the open method.

One variety or another of wool, rendered absorbent by the extraction of its fat, and sterilised by heat, forms a part of almost every surgical dressing, and various antiseptic agents may be added to it.  Of these, corrosive sublimate is the most generally used.  Wood-wool dressings are more highly and more uniformly absorbent than cotton wools.  As evaporation takes place through wool dressings, the discharge becomes dried, and so forms an unfavourable medium for bacterial growth.