SUBLIIMBAR REGION. 205 



Action. — To support and compress the abdominal viscera and 

 assist in respiration. It is the chief flexor of the spinal column. 



TRANSVERSALIS ABDOMINIS. 

 (Lumbo-abdominalis. ) 



Placed on the infero-lateral aspect of the abdomen, imme- 

 diately outside the peritoneum, this muscle is broad, flat, and 

 quadrilateral, its fibres extending downwards. It is fleshy 

 from its origin to the linea semilunaris, where it becomes 

 aponeurotic. 



Attachments. — To the transverse processes of the lumbar 

 vertebrae, and the inner surface of the cartilages of the false ribs, 

 interdigitating with the attachments of the diaphragm, and by 

 its aponeurosis to the xiphoid cartilage and linea alba, becoming 

 rudimentary posteriorly. 



Relations. — Anteriorly with the diaphragm ; externally with 

 the cartilages of the false ribs, the obliquus internus and rectus ; 

 internally with a thin layer of fascia (the fascia transversalis) 

 which connects it with the peritoneum. 



Action. — To assist the oblique muscles, and raise the viscera. 



SUBLUMBAR REGION". 



The muscles of this region, a single group, connect the lumbar 

 and last dorsal vertebrae with the pelvis or the posterior limb. They 

 are covered by the iliac fascia, and this by the peritoneum, a 

 serous membrane lining the abdominal cavity. In this group we 

 place four muscles : — 



Psoas magnus. I Iliacus. 



Psoas parvus. | Quadratus lumborum, 



PSOAS MAGNUS. 



{Sublumbo-trochantineus.) 



(Fig. 76. c.) 



Situated below the transverse processes of the lumbar vertebrae, 

 it is elongated and fusiform, flattened anteriorly, conical posteriorly, 

 its ■ fibres extending downwards and backwards ; it is almost 

 entirely fleshy, except at its insertion. 



Origin. — From the inferior surfaces of the last two ribs, the 



