912 A MANUAL OF ANATOMY 



connection between the anterior wall of the sheath and the tendinous inscrip- 

 tions of the muscle is to be noted at the following levels, namely, at the 

 umbilicus, opposite the tip of the ensiform process, and about midway between 

 these two points. Occasionally a fourth connection is established a little 

 below the umbilicus. The anterior wall of the sheath having been reflected, 

 the pyramidalis muscle should be dissected. If present, it will be found in 

 front of the lower part of the rectus abdominis. The rectus itself is then to 

 be fully dissected. Its two heads of origin and three slips of insertion are 

 to be shown, and the three (sometimes four) tendinous inscriptions are to 

 be studied. The varying relation of the inner border of the muscle to its 

 fellow along the linea alba is to be observed, and both borders of the muscle 

 are to be freed from their connections. In freeing the outer border, the lower 

 five intercostal nerves and the anterior primary division of the twelfth thoracic 

 nerve are to be shown on their way to the back of the muscle (within the 

 sheath). The deep epigastric artery is to be displayed, disappearing beneath 

 the outer border of the muscle at a point about midway between the upper 

 border of the symphysis pubis and the umbilicus. Before further disturbing 

 the muscle, the triangle of Hesselbach is to be studied. It will be found 

 between the lower fourth of the rectus abdominis and the deep epigastric 

 vessels. The relation of the conjoined tendon to the triangle, and the manner 

 in which it divides the triangle into two compartments are to be noted. If 

 the reflected tendon of Cooper should be present, its relation to the triangle 

 is also to be noted. 



The rectus abdominis is now to be raised from its sheath, but not yet 

 divided. As this is being done, the lower five intercostal nerves and the 

 anterior primary division of the twelfth thoracic nerve will be seen making 

 their way from behind forwards through the muscle to become anterior 

 cutaneous nerves. At this stage also the superior epigastric artery is to be 

 shown entering the deep surface of the upper part of the muscle from behind 

 the seventh costal cartilage. The continuation of the deep epigastric artery 

 in the substance of the muscle is to be dissected from behind to a point about 

 2 inches above the umbilicus, and the anastomosis between it and the superior 

 epigastric at that level may be shown. The sheath of the rectus is next to 

 be studied, the muscle itself having been previously divided a little above the 

 umbilicus. The splitting of the internal oblique aponeurosis into two laminae 

 anterior and posterior, along the outer border of the muscle is to be shown. 

 This, however, will be found to cease at a point a little above the level of the 

 anterior superior iliac spine, below which point the undivided aponeurosis 

 will be found to pass in front of the muscle. The anterior aponeurosis of the 

 transversalis abdominis will be seen to pass behind the rectus for a similar 

 extent to that over which the splitting of the internal oblique aponeurosis 

 takes place ; but, over the lower part of the muscle (below a point a little above 

 the level of the anterior superior iliac spine), it passes in front of it. The 

 deficiency of the sheath posteriorly over its lower fourth is to be noted, and 

 the semilunar fold of Douglas, with the deep epigastric artery passing over it, 

 is to be studied. Sometimes the anterior aponeurosis of the transversalis 

 abdominis will be found to send scattered fibres behind the rectus for a 

 variable distance below the semilunar fold of Douglas. In such cases 

 another curved semilunar fold, known as the band of Henle, is to be looked 

 for from i to 2 inches below the semilunar fold of Douglas. The com- 

 position of the sheath in front and behind is to be mastered ; the different 

 attachments superiorly of the anterior and posterior walls are to be noted ; 

 the contents of the sheath are to be studied ; and the linea alba should be 

 thoroughly revised. The dissector should next direct attention to that part 

 of the deep epigastric artery which forms the outer boundary of Hesselbach's 

 triangle, showing its relations to the internal abdominal ring and fascia 

 transversalis, and also its two vena; comites. The cremasteric and pubic 

 branches of the artery are to be shown, but the artery itself is not to be 

 followed, at this stage, to its origin from the external iliac. The deep epi- 

 gastric artery should now be studied throughout its course, its branches should 

 be mastered, and the anastomoses of the vessel should be carefully attended to. 



