Owing to the frequency with which incisional hernia follows the making of an abdominal wound, it would be well that any one engaged, or hoping to be engaged, in the practice of abdominal surgery should have clearly in mind the anatomical structure of the parts through which he will have to pass in order to treat lesions of the viscera whether acute or not. It must be fully recognised, however, that in some acute abdominal conditions it is not always possible, or perhaps wise, to elaborate an incision; the quickest and most direct route must be followed at any cost. Professor F. G. Parsons has kindly made a dissection which he has permitted me to show in this illustration. It gives clearly the relationship of the parts. The rectus muscle appears, however, as usual in the dead subject, more narrow than it is in the living. It then covers two thirds instead of half Of the distance between the anterior superior spine and the umbilicus, as shown. This is important, as will be seen later on. There are certain lines and arrangements Of muscular fibres which must be remembered, and of the former the most important is the linea alba, the second in importance the linea semilunaris.