When the skin—or, in the case of injuries of the base of the skull or the sinuses, the mucous membrane—is broken, a wound is exposed to additional hazards, since the tissues may be invaded by foreign material such as bacteria, dirt, and fragments of clothing, which may give rise to serious local or general complications from infection. Furthermore, if the break in the skin is large, the resulting exposure of the wounded tissues to the drying and cooling effects of the air may increase the damage caused by the wounding agent itself. A needle or a sharp knife that passes ...(100 of 1546 words)