The Pathological condition Arterio-sclerosis has been variously described by different Authors. Savill, in opening a discussion on Arterio- sclerosis before the Pathological Society of London. (Feb: l6. 1904.), said that he was accustomed to define Arterio- sclerosis as a chronic generalised thickening, condensation, or degeneration of the Arterial walls, in which after death, the lumen does not collapse as usual, and the walls are harder and less elastic than normal. Histologically, such a condition may occur in three situations, -in the Tunica media, when it is medial sclerosis, -in the Tunica intima, i.e. Intimal sclerosis, and in the Tunica adventitia, i.e. adventitial sclerosis.