This prolific writer here surveys the diverse opinions of authors respecting the significance of injury in the ætiology of general paralysis, since the first description of the disease by Bayle in 1822, and gives eighty-four references. He considers that injury can act neither as a determining nor as a predisposing cause, and that it is very doubtful whether it can act even as an occasioning cause. Injury can, of course, accelerate or aggravate a pre-existing general paralysis, but it is not certain that it can give rise to the disease, even in a syphilitic subject. On this point, scientifically, an attitude of the greatest reserve is necessary, but for medico-legal purposes it is often right that an injured person should have the benefit of the doubt. The writer sets forth the differential diagnosis between traumatic dementia (strictly so-called) and post-traumatic general paralysis. His account of the medico-legal aspects of the question is mainly of French interest.