274 



DISSECTION OF THE ABDOMEN, 



Fold of 

 Douglas. 



Line* 

 tran sversee 



are three or 

 more; 



situation. 



Linea semi- 

 lunaris is at 

 edge of 

 rectus. 



Pyramidalis 

 muscle : 



attach- 



Nerves in 

 wall of 

 abdomen. 



Intercostal 



are between 

 oblique and 

 transver- 

 salis ; 



offsets. 



Last dorsal 

 nerve. 



umbilicus and pubis, the aponeurosis of the internal oblique ceases 

 to split, and then passes altogether in front of the rectus, with the 

 other aponeuroses. When the rectus is raised, the termination of 

 the hinder layer of the sheath is seen to be marked by a more or less 

 distinct white line, concave towards the pubis, which is termed the 

 semilunar fold of Douglas (fig. 105, p. 286) : below this the rectus is 

 in contact with the traiisversalis fascia. 



The linece transverse^ (fig. 102) on the front of the sheath are 

 caused by the tendinous intersections of the rectus. The most 

 constant are three in number, and have the following position ; one 

 is opposite the umbilicus, another at the lower end of the ensiform 

 process, and the third is midway between the two. If there is a 

 fourth it will be placed below the umbilicus. These markings 

 seldom extend the whole depth or breadth of the muscular fibres, 

 more particularly the highest and lowest. 



Linea semilunaris (fig, 97, p. 263). This line corresponds with the 

 outer edge of the rectus, and reaches from the cartilage of the ninth 

 rib to the pubic spine of the hip-bone : it marks the line of division 

 of the aponeurosis of the internal oblique muscle. 



The PYRAMIDALIS MUSCLE (fig. 102) is triangular in form, and is 

 placed in front of the lower end of the rectus. It arises by its base 

 from the front of the pubis, and is inserted into the linea alba below 

 the mid-point between the umbilicus and the pelvis. This small 

 muscle is often absent. 



Action. The muscle renders tense the linea alba ; and when large 

 it may slightly assist the rectus in compressing the viscera. 



NERVES OF THE ABDOMINAL WALL (fig. 101, p. 271, and fig. 97, 

 p. 263). Between the internal oblique and transversalis muscles 

 are situate the intercostal nerves ; and near the pelvis are two 

 branches of the lumbar plexus, viz., the ilio-hypogastric and ilio- 

 inguinal nerves. Some arteries accompany the nerves, but they 

 will be referred to with the vessels of the abdominal wall 

 (p. 283). 



The LOWER FIVE INTERCOSTAL NERVES enter the wall of the 

 abdomen from the intercostal spaces. Placed between the two 

 deepest lateral muscles, the nerves are directed forwards to the 

 edge of the rectus, and through this muscle to the surface of the 

 abdomen near the middle line. About midway between the spine 

 and the linea alba, the nerves furnish cutaneous branches to the side 

 of the abdomen (lateral cutaneous, p. 262) ; and while between the 

 abdominal muscles they supply branches to them and offsets of 

 communication with one another. A greater part of the lower than 

 of the upper nerves is visible, owing to the shortness of the inferior 



The LAST DORSAL NERVE (fig. 101 ^ is placed below the twelfth rib, 

 and therefore is not in an intercostal space, but it has a similar course 

 and distribution to the foregoing. As it extends forwards to the rectus 

 it communicates sometimes with the ilio-hypogastric nerve ; and its 

 lateral cutaneous branch perforates the two oblique muscles (p. 263). 



