410 MYOLOGY 



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 downward, and are received between corresponding processes of the 

 Serratus anterior; the three lower ones diminish in size from above downward 

 and receive between them corresponding processes from the Latissimus dorsi. 

 From these attachments the fleshy fibers proceed in various directions. Those 

 from the lowest ribs pass nearly ^ vertically downward, and are inserted into the 

 anterior half of the outer lip of the iliac crest; the middle and upper fibers, directed 

 downward and forward, end in an aponeurosis, opposite a line drawn from the 

 prominence of the ninth costal cartilage to the anterior superior iliac spine. 



The aponeurosis of the Obliquus externus abdominis is a thin but strong mem- 

 branous structure, the fibers of which are directed downward and medialward. 

 It is joined with that of the opposite muscle along the middle line, and covers 

 the whole of the front of the abdomen; above, it is covered by and gives origin 

 to the lower fibers of the Pectoralis major; below, its fibers are closely aggregated 

 together, and extend obliquely across from the anterior superior iliac spine to 

 the pubic tubercle and the pectineal line. In the middle line, it interlaces with 

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

 the xiphoid process to the symphysis pubis. 



That portion of the aponeurosis which extends between the anterior superior 

 iliac spine and the pubic tubercle is a thick band, folded inward, and continuous 

 below wdth the fascia lata; it is called the inguinal ligament. The portion which 

 is reflected from the inguinal ligament at the pubic tubercle is attached to the 

 pectineal line and is called the lacunar ligament. From the point of attachment 

 of the latter to the pectineal line, a few fibers pass upward and medialward, behind 

 the medial cms of the subcutaneous inguinal ring, to the linea alba; they diverge 

 as they ascend, and form a thin triangular fibrous band which is called the reflected 

 inguinal ligament. 



In the aponeurosis of the Obliquus externus, immediately above the crest of 

 the pubis, is a triangular opening, the subcutaneous inguinal ring, formed by a 

 separation of the fibers of the aponeurosis in this situation. 



The following structures require further description, viz., the subcutaneous 

 inguinal ring, the intercrural fibers and fascia, and the inguinal, lacunar, and reflected 

 inguinal ligaments. 



The Subcutaneous Inguinal Ring (annulus inguinalis subcutaneus; external 

 abdominal ring) (Fig. 393).- The subcutaneous inguinal ring is an interval in the 

 aponeurosis of the Obliquus externus, just above and lateral to the crest of the 

 pubis. The aperture is oblique in direction, somewhat triangular in form, and 

 corresponds with the course of the fibers of the aponeurosis. It usually measures 

 from base to apex about 2.5 cm., and transversely about 1.25 cm. It is bounded 

 below by the crest of the pubis; on either side by the margins of the opening in the 

 aponeurosis, which are called the crura of the ring ; and above, by a series of curved 

 intercrural fibers. The inferior cms (external pillar) is the stronger and is formed by 

 that portion of the inguinal ligament which is inserted into the pubic tubercle; 

 it is curved so as to form a kind of groove, upon which, in the male, the spermatic 

 cord rests. The superior crus (internal pillar) is a broad, thin, flat band, attached to 

 the front of the symphysis pubis and interlacing with its fellow of the opposite side. 



The subcutaneous inguinal ring gives passage to the spermatic cord and ilio- 

 inguinal nerve in the male, and to the round ligament of the uterus and the 

 ilioinguinal nerve in the female; it is much larger in men than in women, on 

 account of the large size of the spermatic cord. 



The Intercrural Fibers (fibres inter crurales; intercolumnar fibers) . The intercrural 

 fibers are a series of curved tendinous fibers, which arch across the lower part of 



