lood 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.

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 re