It is of much more consequence to avoid injuring the peritoneum. This is sometimes very difficult, from the adhesions which are set up between the peritoneum, the artery, and especially the aneurism, as the result of pressure and inflammation. The accident of wounding the peritoneum has happened to Keate, Tait, Post, and others, and in some cases with perfect impunity. However, the peritoneum should be displaced as little as possible from its cellular connections, as such displacement increases the risk of diffuse inflammation of that membrane; and the vessel itself should be raised and disturbed as little as possible, lest destruction of the vasa vasorum cause ulceration of the weak coats and secondary hæmorrhage. The operation from below (Plate I. fig. 4), SIR ASTLEY COOPER'S, is thus described by Mr. Hodgson:[4]--"A semilunar incision is made through the integuments in the direction of the fibres of the aponeurosis of the external oblique muscle. One extremity of the incision will be situated near the spine of the ilium; the other will terminate a little above the inner margin of the abdominal ring. The aponeurosis of the external oblique muscles will be exposed, and is to be divided throughout the extent, and in the direction of the external wound. The flap which is thus formed being raised, the spermatic cord will be seen passing under the margin of the internal oblique and transverse muscles. The opening in the fascia which lines the transverse muscle through which the spermatic cord passes, is situated in the mid space between the anterior superior spine of the ilium and the symphysis pubis. The epigastric artery runs precisely along the inner margin of this opening, beneath which the external iliac artery is situated. If the finger therefore be passed under the spermatic cord through this opening in the fascia, it will come in immediate contact with the artery which lies on the outside of the external iliac vein. The artery and vein are connected by dense cellular tissue, which must be separated to allow of the ligature being passed round the former."