440 THE MUSCLES AND FA8CIJE 



That form of protrusion in which the intestine follows the course of the spermatic cord along 

 the spermatic canal is called oblique inguinal hernia. 



Surface Form. The only two muscles of this group which have any considerable influence 

 on surface form are the External oblique and the Rectus muscles of the abdomen. With regard 

 to the External oblique, the upper digitations of its origin from the ribs are well marked, and are 

 intermingled with the serrations of the Serratus magnus; the lower digitations are not visible, as 

 they are covered by the thick border of the Latissimus dorsi. The attachment of the External ob- 

 lique to the crest of the ilium, in conjunction with the Internal oblique, forms a thick oblique roll, 

 which determines the iliac furrow. Sometimes on the front of the lateral region of the abdomen 

 an undulating outline marks the spot where the muscle fibres terminate and the aponeurosis 

 commences. The outer border of the Rectus is defined by the linea semilunaris , which may 

 be exactly located by putting the muscle into action. It corresponds with a curved line, with its 

 convexity outward, drawn from the end of the cartilage of the ninth rib to the spine of the os 

 pubis, so that the centre of the line, at or near the umbilicus, is three inches from the median 

 line. The inner border of the Rectus corresponds to the linea alba, marked on the surface of 

 the body by a groove, the abdominal furrow, which extends from the infrasternal fossa to, or to 

 a little below, the umbilicus, where it gradually becomes lost. The surface of the Rectus presents 

 three transverse furrows, the lineae transversae. The upper two of these, one opposite or a 

 little below the tip of the ensiform cartilage, and another, midway between this point and the 

 umbilicus, are usually well marked; the third, opposite the umbilicus, is not so distinct. The 

 umbilicus, situated in the linea alba, varies very much in position as regards its level. It is 

 always situated above a zone drawn around the body opposite the highest point of the crest of 

 the ilium, generally being from three-quarters of an inch to an inch above this line. It usually 

 corresponds, therefore, to the articular disk between the third and fourth lumbar vertebrae. 



2. The Posterior Muscles of the Abdomen. 



Psoas magnus. Iliacus. 



Psoas parvus. Quadratus lumborum. 



The Psoas magnus, the Psoas parvus, and the Iliacus muscles, with the fascia 

 covering them, will be described with the Muscles of the Lower Extremity. 



The Fascia Covering the Quadratus Lumborum (Fig. 327). This is the most 

 anterior of the three layers of the lumbar fascia. It is a thin layer of fascia, which, 

 passing over the anterior surface of the Quadratus lumborum, is attached, inter- 

 nally, to the bases of the transverse processes of the lumbar vertebrae; below, to 

 the iliolumbar ligament; and above, to the apex and lower border of the last 

 rib. 



The portion of this fascia which extends from the transverse process of the 

 first lumbar vertebra to the apex and lower border of the last rib constitutes the 

 ligamentum arcuatum externum. 



The Quadratus lumborum (m. quadratus lumborum} (Fig. 313) is situated in 

 the lumbar region. It is irregularly quadrilateral in shape, and broader below 

 than above. It arises by aponeurotic fibres from the iliolumbar ligament and 

 the adjacent portion of the crest of the ilium for about two inches, and is 

 inserted into the lower border of the last rib for about half its length, and by 

 four small tendons, into the apices of the transverse processes of the four upper 

 lumbar vertebra?. Occasionally a second portion of this muscle is found situ- 

 ated in front of the preceding. This arises from the upper borders of the trans- 

 verse processes of three or four of the lower lumbar vertebrae, and is inserted into 

 the lower margin of the last rib. The Quadratus lumborum is contained in a 

 sheath formed by the anterior and middle lamella' of the lumbar fascia?. 



Relations. Its deep surface (or rather the fascia which covers its anterior surface) is in 

 relation with the colon, the kidney, the Psoas muscle, and the Diaphragm. Between the fascia 

 and the muscle are the last thoracic, iliohvpogastric, and ilioinguinal nerves. Its superficial 

 surface is in relation with the middle lamella of the lumbar fascia, which separates it from the 



