THE ABDOMINAL WALL. 179 
thoracic artery, a branch of the lateral thoracic. The corresponding veins 
are usually conspicuous in the female, since the vessels supply the mam- 
mary glands. A second anastomosis in the cutaneus muscle is formed 
laterally by a branch of the subscapular artery which passes backward 
from the axillary border of the scapula, uniting with an anterior branch 
of the iliolumbar artery. 
The inguinal lymph nodes (lymphoglandulae inguinales) are small, 
oval, brownish bodies lying in the inguinal furrow. 
2. Remove the cutaneus maximus from the surface. Identify 
the following points of attachment of the abdominal muscles proper: 
(a) The linea alba. 
(b) The linea semilunaris, a slightly curved line situated 
laterally a short distance from the linea alba. 
(c) The ribs and the costal arch. 
(d) The lumbodorsal fascia (fascia lumbodorsalis), a broad, 
white sheet of connective tissue extending over the posterior 
thoracic and lumbar regions. 
(e) The inguinal ligament (ligamentum inguinale), a stout 
white cord, stretched between the symphysis pubis and the 
iliac crest. 
3. Identify on the surface the external oblique muscle (m. 
obliquus externus abdominis). Origin: The posterior ten ribs by 
separate slips, the xiphoid process, and the lumbodorsal fascia. 
Insertion: The linea alba and the inguinal ligament. The fibres 
are directed from an anterior dorsal position downward and back- 
ward, the more dorsal ones almost directly backward. Some of the 
anterior slips of origin interdigitate with those of the thoracic 
portion of the serratus anterior muscle. Some are concealed by the 
pectoral muscles. 
The muscle crossing the breast from the sternum-to the arm is the pectoralis 
major. That passing forward from the lumbodorsal fascia to the medial surface of 
the humerus is the latissimus dorsi. “The margins of these muscles may be raised 
where they conceal the external oblique. 
4. Taking a line between the iliac crest and the xiphoid process, 
divide the muscle, and then separate it fully from the next, which 
may be distinguished by the cross direction of its fibres. Note the 
separate slips of origin and the difference in appearance between 
the fleshy portions of the muscle and its ventral tendinous expansion 
or aponeurosis; then remove it from the surface. 
