PRACTICAL CONSIDERATIONS : THE ABDOMEN. 533 



myotomes giving rise to the muscles of the abdomen ; in some of the lower verte- 

 brates (reptiles) these intersections are replaced by bony bars, as seen in the 

 abdominal ribs of crocodiles and some lizards {Haiteria). The highest is about the 

 level of the tip of the ensiform cartilage, the next at that of the tenth rib, the third 

 at the umbilicus. Very rarely a fourth line is seen below this level. The second 

 and third are the most constant, and divide the upper part of each rectus into two 

 nearly quadrilateral portions, easily seen in athletic subjects. These bands tend to 

 prevent overstretching or rupture of the rectus in cases of great abdominal swelling 

 or of violent contraction. The anterior sheath of the rectus is adherent to these 

 fibrous bands. Hence an abscess or a collection of blood on that aspect of the 

 muscle may be confined to the space between any two of them. Posteriorly this is 

 not the case. Spasmodic contraction of the rectus fibres in one of these divisions of 

 the rectus is the cause of one variety of "phantom tumor," the swelling appearing 

 and vanishing with contraction and relaxation of the fibres, — a phenomenon most 

 frequently seen in neurasthenics, but which in this instance may occasionally indicate 

 a reflex disturbance based on some deep-seated source of irritation. Treves has 

 seen, for example, this condition associated with cancer of the stomach, duodenal 

 ulcer, and malignant disease of the peritoneum. 



The higtdnal groove runs with a slight downward curve from the anterior 

 superior iliac spine to the pubic' spine and corresponds to Poupart's ligament. As 

 this latter structure results from a thickening of the lowest fibres of the aponeurosis 

 of the external oblique, and as the internal oblique and transversalis muscles arise 

 from its outer half, it follows that, by reason of its direct continuity with the fascia 

 lata, extension of the thigh on the trunk increases the tension of the anterior 

 abdominal wall. Hence in abdominal examinations the thighs are flexed on the 

 abdomen to lessen this tension. At the same time the shoulders and trunk should 

 be slightly elevated to relax the recti. 



Posteriorly the spinal furrow marks the interval between the erector spinse 

 muscles and the line of attachment of the skin to the tips of the lumbar spines. 

 Farther out the outer edge of the erector spinae is palpable and often visible, except 

 in very fat persons. Occasionally the posterior free edge of the external oblique may 

 be seen when it is not overlapped by the latissimus dorsi. 



4. The 7imbiliciis, except as a landmark, is of chief interest in relation to hernia, 

 in connection with which it will be described. The creases around and between the 

 folds of skin forming the umbilical papilla are difficult to sterilize, and should receive 

 especial attention before operation. 



Fistulae at the umbilicus may be uri7iary and due to a patent urachus (page 191 1), 

 ox fecal, resulting from a persistent vitello-intestinal duct, — Meckel's diverticulum 

 (page 1652). 



5. The Vessels. — The most important artery is the deep epigastric {q.v.), 

 but branches of the deep circumflex iliac, the last two intercostals, and the abdominal 

 branches of the lumbars may require ligation during various abdominal operations. 

 The course of the deep epigastric artery, which is sometimes the source of trouble- 

 some hemorrhage, should be remembered in studying the anterior wall of the 

 abdomen. A line drawn with a slight inward curve from the junction of the inner 

 and middle thirds of Poupart's ligament towards the umbilicus, crossing the outer 

 edge of the rectus muscle about one-third the distance between the level of the sym- 

 physis pubis and that of the navel, will indicate the course of the lower part of this 

 vessel. At the internal abdominal and the femoral rings it has important relations 

 to hernial sacs (page 1493); it lies at first at the side of the rectus in the subserous 

 areolar tissue, then in the transversalis fascia, then within the sheath of the rectus 

 (above the fold of Douglas) behind the middle of the muscle, and finally in the 

 muscle itself. It therefore runs from without inward and becomes more superficial 

 as it ascends. 



With the exception of the superior epigastric and ascending lumbar, all the 

 abdominal and pelvic vems empty directly or indirectly into the inferior vena cava 

 and are therefore affected by the conditions that obstruct that vessel ; hence the 

 superficial veins are often varicose. Although their varicosity is usually a result of 

 obstruction in the portal vein or inferior vena cava, it may occur independently of 



