The vessels of the abdominal walls comprise arteries, veins, and lymphatics. The arteries are superficial and deep; of these the deep are the more important. The arterial twigs in the subcutaneous tissue are small. The superficial epigastric runs in a line from the femoral artery toward the umbilicus. The superficial circumflex iliac runs to its outer side toward the iliac spine, mostly below Poupart's ligament. Branches of these vessels may require the temporary application of a haemostatic forceps in the operations for hernia or appendicitis.

The deep arteries are important: they are the superior epigastric, deep epigastric, and deep circumflex iliac (Fig. 391).

The superior epigastric artery is one of the two terminal branches of the internal mammary. The other is the musculophrenic, which skirts the edge of the thorax. The internal mammary divides opposite the sixth interspace, and the superior epigastric, leaving the thorax at the lower edge of the seventh rib, enters the sheath of the rectus muscle and a few inches lower down enters the substance of the muscle, speedily breaking up into small branches. It is only large in size up toward the thorax, where we have seen it cut by a stab-wound, causing dangerous hemorrhage. It may also be wounded in operations and is to be sought for between the muscle and its posterior sheath, on a line continued downward from a point one centimetre to the outer side of the edge of the sternum.

The deep epigastric artery arises from the external iliac at Poupart's ligament and curves inward and upward between the peritoneum "and transversalis fascia. It reaches the edge of the rectus below a line joining the femoral artery at Poupart's ligament with the umbilicus. Opposite the fold of Douglas (linea semicircular is) it reaches the middle of the rectus, pierces the transversalis fascia, and enters the substance of the muscle. It sends branches to the outer edge of the muscle which are quite large and bleed freely when cut. It anastomoses above with the superior epigastric. It is a most important artery, as it is liable to be wounded in operations for appendicitis, etc. If cut it will require a ligature, and if pierced by a needle will bleed freely. As it passes upward from Poupart's ligament it lies to the upper and outer side of the femoral canal and may be wounded if the herniotomy knife is turned in that direction. A little higher it crosses the inguinal canal almost midway between the internal and external abdominal rings. An oblique inguinal hernia enters the canal to the outer side of this artery and a direct hernia to its inner side. The fold of the obliterated hypogastric artery is to its inner side.

Fig. 391.   The nerves and blood vessels of the anterior abdominal wall. The nerves are seen piercing the posterior layer of the sheath of the rectus to enter the muscle. The external and internal oblique have been removed exposing the nerves lying on the transversalis.

Fig. 391. - The nerves and blood-vessels of the anterior abdominal wall. The nerves are seen piercing the posterior layer of the sheath of the rectus to enter the muscle. The external and internal oblique have been removed exposing the nerves lying on the transversalis.

The deep circumflex iliac artery arises from the external iliac almost opposite the deep epigastric and passes outward along the inner side of Poupart's ligament between the transversalis fascia and the peritoneum. When it reaches the anterior superior spine it passes between the transversalis and internal oblique muscles, and just above the crest divides into an ascending branch which goes upward toward the ribs and a posterior branch passing backward to anastomose with the iliolumbar. The ascending branch is large and bleeds freely when cut. It is not infrequently divided in operations for appendicitis in which the incision is carried far back. Its depth from the surface, between the transversalis and internal oblique muscles, should not be forgotten.