396 THE MUSCULAR SYSTEM. 
origins; the musculo-phrenic artery passes between the attachments to the seventh 
and eighth ribs. The sympathetic cord and the splanchnic nerves pierce or pass 
behind the diaphragm; the last thoracic nerve passes beneath the external arcuate 
ligament; and the aorta, the vena azygos major and thoracic duct pass between 
the crura, beneath the middle arcuate ligament (aortic opening). The special — 
foramina are two in number. The foramen quadratum in the right lobe of the | 
central tendon transmits the inferior vena cava, and small branches of the right — 
Vena caval opening Misophageal opening Central tendon (middle part) 
; 
¥ 
zt 
eS RIGHT CRUS | 
_ Middle arcuate ligamen 
6 _7 Aortic opening 
~ (left part) 
DIAPHRAGM, LEFT 
CRUS 
Central tendon 
i 
Central tendon (right part) 
DIAPHRAGM, COSTAL FIBRES 4 ZEEE a | iN ANY CUNY ~ | 
Internal arcuate ligament Flay 
ti 
External arcuate ligament ‘ 
End of last rib Last thoracic nerve | 
Last thoracie nerve End of last rib 
| 
; nf cage sumbar nerve L[. 
Ant. layer of lumbar fascia = B i I nbar WENI® P 
4 / Mant a \ —— ia ~hu eastric 
Lumbar fascia E Wott } lio-hypogastric | 
/ —Lumbar nerve IT. 
Tlio-hypogastric 
Linbar vessels and sympa- 
thetic communicating nerves” 
Tlio-inguinal 
Llio-inguinal 5 
QUADRATUS : 
LUMBORUM t 
Lumbar nerve III 
QUADRATUS LUMBORUM- 
Genito-crural 
External cutaneous nerve Lumbar nerve IV. 
Psoas Maanus£ 
IL1acus 
Lumnbo-sacral cord Lumbo-sacral cord 
Anterior crural nerve VI ii ey BS Y/ 3 External cuteness nerve 
Obturatonmene rit AN Ig) \ ae Anterior crural nerve 
Be Hl ih if oT y 2s 3s Obturator nerve { 
Great sciatic nerve j Ty A ’ res Great sciatic nerve } 
; 
¢ 
/ 
' 
| H Obturator nerve 
| ADDUCTOR LONGUS (origin) 
| ADDUCTOR BREVIS (origin) ' 
GRACILIS (origin)} nh 
| ADDUCTOR MAGNUS (origin) 
PECTINEUS (cut) j 
Superficial branch of obturator nerve r} 
Deep branch of obturator nerve 
OBTURATOR EXTERNUS 
Fie. 291.—VIEW OF THE POsTERIOR ABDOMINAL WALL, TO SHOW THE MUSCLES AND THE NERVES OF 
THE LUMBO-SACRAL PLEXUS. 
phrenic nerve. The wsophageal opening is in the muscular substance of the 
diaphragm, behind the central tendon, and is surrounded by a sphincter-like 
arrangement of the crural fibres. Besides the cesophagus, this opening transmits 
the two pneumogastric nerves. The upper convex surface of the diaphragm forms ~ 
the sloping floor of the thorax, and is in contact with the pleure, and the peri- 
eardium (which is firmly bound down to the central tendon, and less firmly to the 
