The clinical features of this condition are practically the same as those of shock; and it is treated on the same lines.

FAT EMBOLISM.—­After various injuries and operations, but especially such as implicate the marrow of long bones—­for example, comminuted fractures, osteotomies, resections of joints, or the forcible correction of deformities—­fluid fat may enter the circulation in variable quantity.  In the vast majority of cases no ill effects follow, but when the quantity is large or when the absorption is long continued certain symptoms ensue, either immediately, or more frequently not for two or three days.  These are mostly referable to the lungs and brain.

In the lung the fat collects in the minute blood vessels and produces venous congestion and oedema, and sometimes pneumonia.  Dyspnoea, with cyanosis, a persistent cough and frothy or blood-stained sputum, a feeble pulse and low temperature, are the chief symptoms.

When the fat lodges in the capillaries of the brain, the pulse becomes small, rapid, and irregular, delirium followed by coma ensues, and the condition is usually rapidly fatal.

Fat is usually to be detected in the urine, even in mild cases.

The treatment consists in tiding the patient over the acute stage of his illness, until the fat is eliminated from the blood vessels.

TRAUMATIC ASPHYXIA OR TRAUMATIC CYANOSIS.—­This term has been applied to a condition which results when the thorax is so forcibly compressed that respiration is mechanically arrested for several minutes.  It has occurred from being crushed in a struggling crowd, or under a fall of masonry, and in machinery accidents.  When the patient is released, the face and the neck as low down as the level of the clavicles present an intense coloration, varying from deep purple to blue-black.  The affected area is sharply defined, and on close inspection the appearance is found to be due to the presence of countless minute reddish-blue or black spots, with small areas or streaks of normal skin between them.  The punctate nature of the coloration is best recognised towards the periphery of the affected area—­at the junction of the brow with the hairy scalp, and where the dark patch meets the normal skin of the chest (Beach and Cobb).  Pressure over the skin does not cause the colour to disappear as in ordinary cyanosis.  It has been shown by Wright of Boston, that the coloration is due to stasis from mechanical over-distension of the veins and capillaries; actual extravasation into the tissues is exceptional.  The sharply defined distribution of the coloration is attributed to the absence of functionating valves in the veins of the head and neck, so that when the increased intra-thoracic pressure is transmitted to these veins they become engorged.  Under the conjunctivae there are extravasations of bright red blood; and sublingual haematoma has been observed (Beatson).

The discoloration begins to fade within a few hours, and after the second or third day it disappears, without showing any of the chromatic changes which characterise a bruise.  The sub-conjunctival ecchymosis, however, persists for several weeks and disappears like other extravasations.  Apart from combating the shock, or dealing with concomitant injuries, no treatment is called for.