nfection, not only in dealing with wounds that
are free of organisms, but equally in the management of wounds and other
lesions that are already infected. Any laxity in our methods which
admits of fresh organisms reaching an infected wound adds materially to
the severity of the infective process and consequently to the patient's
risk.

There are many ways in which accidental infection may occur. Take, for
example, the case of a person who receives a cut on the face by being
knocked down in a carriage accident on the street. Organisms may be
introduced to such a wound from the shaft or wheel by which he was
struck, from the ground on which he lay, from any portion of his
clothing that may have come in contact with the wound, or from his own
skin. Or, again, the hands of those who render first aid, the water used
to bathe the wound, the handkerchief or other extemporised dressing
applied to it, may be the means of conveying bacterial infection. Should
the wound open on a mucous surface, such as the mouth or nasal cavity,
the organisms constantly present in such situations are liable to prove
agents of infection.

Even after the patient has come under professional care the risks of his
wound becoming infected are not past, because the hands of the doctor,
his instruments, dressings, or other appliances may all, unless
purified, become the sources of infection.

In the case of an operation carried out through unbroken skin, organisms
may be introduced into the wound from the patient's own skin, from the
hands of the surgeon or his assistants, through the medium of
contaminated instruments, swabs, ligature or suture materials, or other
things used in the course of the operation, or from the dressings
applied to the wound.

Further, bacteria may gain access to devitalised tissues by way of the
blood-stream, being carried hither from some infected area elsewhere in
the body.

_The Antiseptic System of Surgery._--Those who only know the surgical
conditions of to-day can scarcely realise the state of matters which
existed before the introduction of the antiseptic system by Joseph
Lister in 1867. In those days few wounds escaped the ravages of pyogenic
and other bacteria, with the result that suppuration ensued after most
operations, and such diseases as erysipelas, pyaemia, and "hospital
gangrene" were of everyday occurrence. The mortality after compound
fractures, amputations, and many other operations was appalling, and