THE DIAPHRAGMATIC REGION. 



445 



the other end. to the front of the transverse process of the first, and sometimes 

 also to that of the second, lumbar vertebra. 



The U'!<iin> ittiini <ir<-ii<itiiii( externum is the thickened upper margin of the ante- 

 rior lamella of the lumbar fascia : it arches across the upper part of the Quadratus 

 lumborum, being attached, by one extremity, to the front of the transverse process 

 of the first, sometimes also of the second, lumbar vertebra, and, by the other, to 

 the apex and lower margin of the last rib. 



The Crura The Diaphragm is connected to the spine by two crura or pillars, 

 which are situated on the bodies of the lumbar vertebrae, on each side of the aorta. 

 The crura. at their origin, are tendinous in structure ; the right crus, larger and 

 longer than the left, arising from the anterior surface of the bodies and inter- 

 vertebral substances of the three or four upper lumbar vertebras ; the left, from 



FIG. 290. The Diaphragm. Under surface. 



the two upper : both blending with the anterior common ligament of the spine. 

 These tendinous portions of the crura pass forward and inward, and gradually 

 converge to meet in the middle line, forming an arch, beneath which passes the 

 aorta, vena azygos major, and thoracic duct. From this tendinous arch muscular 

 fibres arise, which diverge, the outermost portion being directed upward and 

 outward to the central tendon : the innermost decussating in front of the aorta, 

 and then diverging, so as to surround the oesophagus before ending in the central 

 tendon. The fibres derived from the right crus are the most numerous and pass 

 in front of those derived from the left. 



The Central or Cordifrtn 7'< /,,/<> of the Diaphragm is a thin but strong 

 tendinous aponeurosis, situated at the centre of the vault formed by the muscle, 

 immediately below the pericardium, with which its upper surface is blended. It 

 is shaped somewhat like a trefoil leaf, consisting of three divisions, or leaflets, 



