MUSCLES OP THE ABDOMEN. 



549 



the subclavian to supply the anterior abdominal walls. 

 Each artery has one or two accompanying veins which 

 open into the femoral, saphena, iliac, and subclavian veins- 



The nerves come principally from the lumbar plexus. 



The posterior walls of the abdomen include muscles, fas- 

 cia, blood-vessels, nerves, and lumbar vertebrse. 



The muscles are quadratus lumborum, psoas magnus, 

 psoas parvus, iliacus internus. 



The quadratus lumborum, situated between the last rib 

 and the ilium, and composing a great part of the poste- 

 rior abdominal wall, is FIG. 172. 

 enclosed in a strong 

 sheath, formed of the 

 middle and anterior 

 layers of the tendon of 

 the transverse muscle. 

 By removing the ante- 

 rior layer of this sheath 

 with the colon and kid- 

 ney, the muscle is ex- 

 posed. It presents an 

 oblong form, and arises 

 tendinous and fleshy 

 from the posterior crest 

 of the ilium and ilio 

 lumbar ligament, and 

 ascends to be inserted 

 into the transverse pro- 

 cesses of the last dorsal 

 and four upper lumbar 

 vertebrae by tendinous 

 slips, and into the ver- 

 tebral half of the last 

 rib. Function. To aid in expiration, by drawing down 

 the last rib, and flexing the spine to one side. 



FIG. 172 represents Muscles of the posterior wall of Abdomen, a Quadratus 

 lumborum. 6 Iliacus internus. c Psoas-magnus. d Psoas parvus. t Obtu- 

 rator externus. 



