252 THE ABDOMEN AND PELVIS 



of the horizontal part of the incision. When this has been done, 

 the anterior wall of the sheath and the rectus may be cut across 

 between the two rows of sutures, which serve to prevent 

 retraction of the cut ends of the muscle A large triangular 

 musculo-cutaneous flap can then be turned upwards and to 

 the right, until the terminal parts of the intercostal nerves are 

 exposed as they pass forwards into the rectus. The posterior 

 wall of the sheath, together with the underlying transversalis 

 fascia and parietal peritoneum, is divided by an oblique incision, 

 which is placed medial to the nerves and nearly parallel to the 

 costal margin. 



This method of approach, while providing good access to 

 the region of the gall-bladder, produces little weakening of the 

 abdominal wall, since none of the motor nerves are injured. In 

 addition there is little danger of the occurrence of a post-operative 

 hernia, as the anterior and posterior walls of the rectus sheath are 

 not divided in the same line. 



An incision, of varying length, two inches below and 

 parallel to the right costal margin, gives good access to the 

 gall-bladder. In obese subjects it may be necessary to prolong 

 the lateral part of the incision in a downward direction. If, 

 during this operation, the lower part of the patient's back is 

 supported by a sand-bag, pillow, etc., the forward convexity of 

 the lumbar region is increased, the viscera are pressed forwards, 

 and the wound gapes so as to afford excellent access. Incisions 

 planned to preserve the nerves, i.e. made at right angles to the 

 costal margin, cannot be made to gape in the same way. 



In all cases where the abdominal muscles are cut across the 

 direction of their fibres, the wall must be sewn up in layers to 

 diminish the subsequent weakness as far as possible. 



The Transversalis Fascia covers the deep surface of the 

 transversus muscle, and, inferiorly, it extends beyond the lower 

 border of the muscle to reach the inguinal ligament. It extends 

 medially behind the posterior wall of the rectus sheath, with 

 which it partially blends. In the lower part of the anterior 

 abdominal wall, where the rectus sheath is deficient posteriorly, 

 the transversalis fascia lies in direct contact with the rectus 

 abdominis. Above, it is continuous with the fascia on the under 

 surface of the diaphragm, and below with the pelvic fascia. 

 The connections of the transversalis fascia on the posterior 

 abdominal wall are described on p. 271. 



Arteries of the Anterior Abdominal Wall. 



