CONTUSIONS—­WOUNDS:  Varieties—­WOUNDS BY FIREARMS AND
    EXPLOSIVES:  Pistol-shot wounds; Wounds by sporting guns;
    Wounds by rifle bullets; Wounds received in warfare; Shell
    wounds. Embedded foreign bodies—­BURNS AND
    SCALDS—­INJURIES PRODUCED BY ELECTRICITY:  X-ray and
    radium; Electrical burns; Lightning stroke.

CONTUSIONS

A contusion or bruise is a laceration of the subcutaneous soft tissues, without solution of continuity of the skin.  When the integument gives way at the same time, a contused-wound results.  Bruising occurs when force is applied to a part by means of a blunt object, whether as a direct blow, a crush, or a grazing form of violence.  If the force acts at right angles to the part, it tends to produce localised lesions which extend deeply; while, if it acts obliquely, it gives rise to lesions which are more diffuse, but comparatively superficial.  It is well to remember that those who suffer from scurvy, or haemophilia (bleeders), and fat and anaemic females, are liable to be bruised by comparatively trivial injuries.

Clinical Features.—­The less severe forms of contusion are associated with ecchymosis, numerous minute and discrete punctate haemorrhages being scattered through the superficial layers of the skin, which is slightly oedematous.  The effused blood is soon reabsorbed.

The more severe forms are attended with extravasation, the extravasated blood being widely diffused through the cellular tissue of the part, especially where this is loose and lax, as in the region of the orbit, the scrotum and perineum, and on the chest wall.  A blue or bluish-black discoloration occurs in patches, varying in size and depth with the degree of force which produced the injury, and in shape with the instrument employed.  It is most intense in regions where the skin is naturally thin and pigmented.  In parts where the extravasated blood is only separated from the oxygen of the air by a thin layer of epidermis or by a mucous membrane, it retains its bright arterial colour.  These points are often well illustrated in cases of black eye, where the blood effused under the conjunctiva is bright red, while that in the eyelids is almost black.  In severe contusions associated with great tension of the skin—­for example, over the front of the tibia or around the ankle—­blisters often form on the surface and constitute a possible avenue of infection.  When deeply situated, the blood tends to spread along the lines of least resistance, partly under the influence of gravity, passing under fasciae, between muscles, along the sheaths of vessels, or in connective-tissue spaces, so that it may only reach the surface after some time, and at a considerable distance from the seat of injury.  This fact is sometimes of importance in diagnosis, as, for example, in certain fractures of the base of the skull, where discoloration appears under the conjunctiva or behind the mastoid process some days after the accident.