OF THE ABDOMEN. 357 



abdomen. It arises, by eight fleshy digitations, from the external surface and 

 lower borders of the eight inferior ribs; these digitations are arranged in an 

 oblique line running downward and backward ; the upper ones being attached 

 close to the cartilages of the corresponding ribs ; the lowest, to the apex of the 

 cartilage of the last rib ; the intermediate ones, to the ribs at some distance from 

 their cartilages. The five superior serrations increase in size from above down- 

 ward, and are received between corresponding processes of the Serratus magnus ; 

 the three lower ones diminish in size from above downward, receiving between 

 them corresponding processes from the Latissimus dorsi. From these attachments, 

 the fleshy fibres proceed in various directions. Those from the lowest ribs pass 

 nearly vertically downward, to be inserted into the anterior half of the outer lip 

 of the crest of the ilium ; the middle and'upper fibres, directed downward and for- 

 ward, terminate in an aponeurosis, opposite a line drawn from the prominence of 

 the ninth costal cartilage to the anterior superior spinous process of the ilium. 



The Aponeurosis of the External Oblique is a thin, but strong membranous 

 aponeurosis, the fibres of which are directed obliquely downward and inward. It 

 is joined with that of the opposite muscle along the median line, covers the 

 whole of the front of the abdomen ; above, it is connected with the lower border 

 of the Pectoralis major ; below, its fibres are closely aggregated together, and 

 extend obliquely across from the anterior superior spine of the ilium to the spine 

 of the os pubis and the linea ilio-pectinea. In the median line it interlaces Avith 

 the aponeurosis of the opposite muscle, forming the linea alba, which extends from 

 the ensiform cartilage to the symphysis pubis. 



That portion of the aponeurosis which extends between the anterior superior 

 spine of the ilium and the spine of the os pubis is a broad band, folded inward, 

 and continuous below with the fascia lata ; it is called Poupart's ligament. The 

 portion which is reflected from Poupart's ligament at the spine of the os pubis 

 along the pectineal line is called Grimbernat's ligament. From the point of attach- 

 ment of the latter to the pectineal line, a few fibres pass upward and inward, 

 behind the inner pillar of the ring, to the linea alba. They diverge as they ascend, 

 and form a thin, triangular, fibrous layer, which is called the triangular fascia of 

 the abdomen. 



In the aponeurosis of the External oblique, immediately above the crest of the 

 os pubis, is a triangular opening, the external abdominal ring, formed by a separa- 

 tion of the fibres of the aponeurosis in this situation. 



Relations. By its external surface, Avith the superficial fascia, superficial 

 epigastric and circumflex iliac vessels, and some cutaneous nerves ; by its internal 

 surface, with the Internal oblique, the lower part of the eight inferior ribs, and 

 Intercostal muscles, the Cremaster, the spermatic cord in the male, and round liga- 

 ment in the female. Its posterior border, extending from the last rib to the crest 

 of the ilium, is fleshy throughout and free ; it is occasionally overlapped by the 

 Latissimus dorsi, though generally a triangular interval exists between the two 

 muscles near the crest of the ilium, in which is seen a portion of the internal 

 oblique. This triangle, Petit's triangle, is therefore bounded in front by the 

 External oblique, behind by the Latissimus dorsi, below by the crest of the ilium, 

 while its floor is formed by the Internal oblique (Fig. 213). 



The following parts of the aponeurosis of the External oblique muscle require 

 to be further described : viz., the external abdominal ring, the intercolumnar fibres 

 and fascia, Poupart's ligament, Gimbernat's ligament, and the triangular fascia 

 of the abdomen. 



The External Abdominal Ring. Just above and to the outer side of the crest 

 of the os pubis an interval is seen in the aponeurosis of the External oblique, 

 called the -External Abdominal Ring. The aperture is oblique in direction, some- 

 what triangular in form, and corresponds with the course of the fibres of the 

 aponeurosis. It usually measures from base to apex about an inch, and 

 transversely about half an inch. It is bounded below by the crest of the os 

 pubis ; above, by a series of curved fibres, the intercolumnar, which pass across 



