Blood extravasated deeply in the tissues gives rise to a firm, resistant, doughy swelling, in which there may be elicited on deep palpation a peculiar sensation, not unlike the crepitus of fracture.

It frequently happens that, from the tearing of lymph vessels, serous fluid is extravasated, and a lymphatic or serous cyst may form.

In all contusions accompanied by extravasation, there is marked swelling of the area involved, as well as pain and tenderness.  The temperature may rise to 101 F., or, in the large extravasations that occur in bleeders, even higher—­a form of aseptic fever.  The degree of shock is variable, but sudden syncope frequently results from severe bruises of the testicle, abdomen, or head, and occasionally marked nervous depression follows these injuries.

Contusion of muscles or nerves may produce partial atrophy and paresis, as is often seen after injuries in the region of the shoulder.

In alcoholic or other debilitated patients, suppuration is liable to ensue in bruised parts, infection taking place from cocci circulating in the blood, or through the overlying skin.

Terminations of Contusions.—­The usual termination is a complete return to the normal, some of the extravasated blood being organised, but most of it being reabsorbed.  During the process characteristic alterations in the colour of the effused blood take place as a result of changes in the blood pigment.  In from twenty-four to forty-eight hours the margins of the blue area become of a violet hue, and as time goes on the discoloured area increases in size, and becomes successively green, yellow, and lemon-coloured at its margins, the central part being the last to change.  The rate at which this play of colours proceeds is so variable, and depends on so many circumstances, that no time-limits can be laid down.  During the disintegration of the effused blood the adjacent lymph glands may become enlarged, and on dissection may be found to be pigmented.  Sometimes the blood persists as a collection of fluid with a newly formed connective-tissue capsule, constituting a haematoma or blood cyst, more often met with in the scalp than in other parts.

The impairment of the blood supply of the skin may lead to the formation of blisters, or to necrosis.  Death of skin is more liable to occur in bleeders, and when the slough separates the blood-clot is exposed and the reparative changes go on extremely slowly. Suppuration may occur and lead to the formation of an abscess as a result of direct infection from the skin or through the circulation.

Treatment.—­If the patient is seen immediately after the accident, elevation of the part, and firm pressure applied by means of a thick pad of cotton wool and an elastic bandage, are useful in preventing effusion of blood.  Ice-bags and evaporating lotions are to be used with caution, as they are liable to lower the vitality of the damaged tissues and lead to necrosis of the skin.