364 



THE MUSCLES AND FASCIAE 



blending with the aponeurosis of the External oblique : the other, behind it, 

 blending with the aponeurosis of the Transversalis ; and these, joining again at its 

 inner border, are inserted into the linea alba. This arrangement of the aponeuroses 

 exists along the upper three-fourths of the muscle : at the commencement of the 

 lower fourth, the posterior wall of the sheath terminates in a thin curved margin, 

 the semilunar fold of Douglas, the concavity of Avhich looks downward toward 

 the pubes ; the aponeuroses of all three muscles passing in front of the Rectus 

 without any separation. The extremities of the fold of Douglas descend as pillars 

 to the os pubis. The inner pillar is attached to the symphysis pubis ; the outer 

 pillar, which is named by .Braune the ligament of Ilesselbach, passes downward as 

 a distinct band on the inner side of the internal abdominal ring, and there its 

 fibres divide into two sets, internal and external ; the internal fibres are attached 

 to the ascending ramus of the os pubis and the pectineal fascia ; the external ones 

 pass to the Psoas fascia, to the deep surface of Poupart's ligament, and to the 

 tendon of the Transversalis on the outer side of the ring. The Rectus muscle, in 

 the situation Avhere its sheath is deficient, is separated from the peritoneum by the 

 trans versalis fascia. 



FIG. 221. A transverse section of the abdomen in the lumbar region. 



The Pyramidalis is a small muscle, triangular in shape, placed at the lower 

 part of the abdomen, in front of the Rectus, and contained in the same sheath 

 with that muscle. It arises by tendinous fibres from the front of the os pubis 

 and the anterior pubic ligament ; the fleshy portion of the muscle passes upward, 

 diminishing in size as it ascends, and terminates by a pointed extremity, which is 

 inserted into the linea alba, midway between the umbilicus and the os pubis. This 

 muscle is sometimes found wanting on one or both sides ; the lower end of the 

 Rectus then becomes proportionately increased in size. Occasionally it has been 

 found double on one side, or the muscles of the two sides are of unequal size. 

 Sometimes its length exceeds what is stated above. 



Besides the Rectus and Pyramidalis muscles, the sheath of the Rectus contains 

 the superior arid deep epigastric arteries, the terminations of the lumbar arteries 

 and of the lower intercostal arteries and nerves. 



Nerves. The abdominal muscles are supplied by the lower intercostal nerves. 

 The Transversalis and Internal oblique also receive filaments from the hypogastric 

 branch of the ilio-hypogastric and sometimes from the ilio-inguinal. The Cremaster 

 is supplied by the genital branch of the Genito-crural. 



In the description of the abdominal muscles mention has frequently been made 

 of the linea alba, linese semilunares, and linese transversae ; when the dissection of 

 the muscles is completed these structures should be examined. 



