384 ABDOMEN 



The superficial epigastric takes a vertical course upwards, 

 and, crossing the inguinal ligament, ramifies in the superficial 

 fascia over the lower part of the abdomen. Its branches 

 extend as high as the level of the umbilicus. 



The small veins which accompany these arteries open into 

 the large saphenous vein. 



Muscles of the Abdominal Wall. The abdominal wall is 

 formed anteriorly and laterally by five pairs of muscles, and by 

 the aponeuroses which constitute their tendons. Anteriorly 

 are the two recti muscles and the two pyramidales muscles. 

 The recti are placed parallel to the middle line, and extend 

 in a vertical direction from the pubic bones to the lower 

 margin of the thorax. On each side three fleshy and apon- 

 eurotic strata are met with. From the surface towards the 

 abdominal cavity they are (i) the external oblique muscle; 

 (2) the internal oblique muscle ; (3) the transversus abdominis 

 muscle. The direction taken by the muscular fibres which 

 compose each of these layers is different. The external 

 oblique corresponds in this respect with the external inter- 

 costal muscles ; the fibres proceed obliquely downwards and 

 forwards. Again, the internal oblique resembles the internal 

 intercostal muscles in the direction of its fibres ; they are 

 directed upwards and forwards, and thus the fibres of the 

 two oblique muscles cross each other like the limbs of the 

 letter X. Lastly, the fibres composing the transversus 

 abdominis muscle pursue a horizontal or transverse course. 



This difference of direction in the fibres which compose 

 these three strata is a source of strength to the fleshy part of 

 the abdominal wall, which, consequently, offers a strong barrier 

 to the protrusion of any of the abdominal contents. The 

 two oblique muscles and the transversus are prolonged to 

 the middle line in the form of aponeuroses. The union 

 of these with the corresponding aponeuroses of the opposite 

 side forms the linea alba a strong band which extends, in 

 the median line, from the symphysis pubis to the xiphoid 

 process. 



Dissection. Remove the superficial fascia from the front of the abdomen. 

 This will expose the aponeurosis of the external oblique muscle. Towards 

 the thorax this aponeurosis is very thin, and is liable to injury, unless the 

 dissection be performed with care. Proceed cautiously also at the lower 

 part of the abdomen, above the medial end of the inguinal ligament. Here 

 the aponeurosis is pierced in the male by the spermatic cord. The lips of 

 the opening thus formed are prolonged downwards upon the cord in the 



