being soaked for twelve hours in ether, for other
twelve in alcohol, and then boiled for ten minutes in 1 in 1000
sublimate solution. It is then wound on spools with purified hands
protected by sterilised gloves, and kept in absolute alcohol. Before an
operation the silk is again boiled for ten minutes in the same solution,
and is used directly from this (Kocher). Linen thread is sterilised in
the same way as silk.

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 w