OF THE ABDOMEN. 



455 



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 which 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 Hesselbach, divides below to 

 enclose the internal abdominal ring; the internal fibres are attached to the 

 horizontal ramus of the os pubis and the pectineal fascia ; the external ones pass 

 to the Psoas fascia and to the Transversalis where it arises from Poupart's 

 ligament on the outer side of the ring. The Rectus muscle, in the situation 



FIG. 203. A Transverse section of the abdomen in the lumbar region. 



where its sheath is deficient, is separated from the peritoneum by the transversalis 

 fascia. 



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. 



Eelations. Its anterior surface is covered by the sheath of the Rectus. Its 

 jiotten'or surface rests against the Rectus itself. To expose the Pyramidalis, 

 make, through the sheath of the Rectus. a vertical incision the lower end of 

 which should begin just a little to one side of. and on a level with, the symphysis 

 pubi*. 



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

 The Internal oblique also receives a filament from the ilio-inguinal nerve. 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, lineae semilunares, and linere transversae ; when the dissection of 

 the muscles is completed these structures should be examined. 



The linea alba is a tendinous raphe seen along the middle line of the abdomen, 

 extending from the ensiform cartilage to the symphysis pubis, to which it is 



