216 ABDOMEN 



has not attained the dignity of a name, it is a very constant 

 branch. On the right side the fibres springing from the inguinal 

 ligament should also be severed, but on the left side carry the 

 knife horizontally, from the anterior superior spine of the ilium 

 to the lateral margin of the rectus. Now turn to the upper part 

 of the muscle, and make an incision through it, along the lower 

 margin of the thorax, from the lateral border of the rectus to 

 the last rib. Lastly, carry the knife downwards, from the tip 

 of the last rib to the crest of the ilium. 



The muscle freed in this manner can be reflected medially 

 towards the lateral border of the rectus, but the dissector must 

 proceed with caution, because he has reached the plane of the 

 main trunks of the nerves of the abdominal wall and the arteries 

 which accompany them. The nerves and vessels pass medially 

 between the internal oblique and the transverse muscles, and, 

 as the former muscle is raised, they are apt to adhere to its deep 

 surface and will be cut if proper care is not exercised. 



In all probability the student will experience considerable 

 difficulty in separating the lowest part of the internal oblique 

 from the corresponding portion of the transversus abdominis, 

 for the lower parts of the two muscles are always closely con- 

 nected, and in some cases they are partially blended. 



On the right side the cremaster muscle should also be reflected 

 from the spermatic cord. That can best be done by making a longi- 

 tudinal incision through its fibres. Entering the deep surface of 

 the cremaster are a small branch of the inferior epigastric artery 

 and the external spermatic nerve (a branch of the genito-femoral) . 

 They constitute its vascular and nervous supply, and must, if 

 possible, be secured. Now clean the transversus abdominis 

 muscle, and the vessels and nerves which lie upon it. 



Nerves of the Abdominal Wall. The dissector will find 

 the following nerves running forwards upon the transversus 

 abdominis muscle : 



1. The anterior branches of the lower six thoracic nerves. 



2. The ilio-hypogastric nerve. \From the anterior ramus of the first 



3. The ilio-inguinal nerve. / lumbar nerve. 



The anterior branches of the lower six thoracic nerves enter 

 the abdominal wall at the margin of the costal arch, where 

 they insinuate themselves between the internal oblique and 

 the transversus abdominis muscles. Then they run to the 

 lateral border of the rectus muscle, where they disappear by 

 piercing the posterior lamella of the internal oblique 

 aponeurosis, and passing within the sheath of the rectus. 

 In a subsequent dissection they will be seen sinking into the 

 substance of the rectus, supplying it with twigs, and then 

 turning forwards to pierce the front of the sheath. They 

 end on the front of the abdomen as the anterior cutaneous 

 nerves. They supply offsets to the internal oblique and also 



