Cerebral and retinal fat emboli in normal animals fixed by perfusion

The brains and retinas of laboratory animals fixed by perfusion occasionally contain isolated round fat emboli, which increase in number if the two organs are covered with oil during the autopsy. These emboli, in contrast to emboli induced by intravenous injection of oil, are present in smaller numbers, occur without adjacent aggregation of erythrocytes and do not cause widening of the occluded vascular channel. The fat emboli in the normal brain are attributed to connective tissue fat aggregating on the exposed cerebral surface and flowing through openings cut in the leptomeninges and the vascular walls during removal of the brain. Their formation could not be entirely prevented by covering the brain with running water or by submerging the forepart of the animal's body in water during the autopsy. Nevertheless, such a procedure is recommended to avoid introduction of extraneous fat when in a given experiment the question of fat embolism arises. Fat emboli demonstrable in the flattened retina of the cat and the mulatta monkey are ascribed to aspiration of retrobulbar connective tissue fat; they can be prevented by placing a ligature around the optic nerve prior to removal of the eye.