This is a condition in which the choroid plexuses of the ventricles are infiltrated with fluid which has escaped from the fine net-work of veins of which they are mainly composed. So far as is known it is of somewhat rare occurrence. It may, however, be more common than is generally supposed, were post-mortem examinations more frequently made of the brain in those cases where death follows upon sudden and complete coma.

The causes of oedema of the choroid plexuses is not well established, but in the case of which an illustration is here given (see Coloured Plate) the horse had been the subject of influenza, and appeared to be making a good recovery. He was, however, suddenly seized with dulness, followed by deep coma, and death occurred twenty-four hours later.

Post-mortem examination showed clots of coagulated blood obstructing the veins leading from the plexuses into the veins of Galen.

There was nothing either in the history of the case, or in the postmortem inspection, to show why the blood should have clotted and obstructed the circulation in these veins. A blow on the head in such circumstances might have caused it, or it may have resulted from some change in the blood consequent on the disease.

Where, as in this instance, the choroid plexuses were torn up, treatment could be of little avail.