THE DIAPHRAGM. 



309 



The fibres arise from the bodies of several of the upper lumbar 

 vertebrte by two thick crura ; from two arches on each side external to 

 the bodies of the vertebrte, called ligamenta arcuata ; and from the 

 ensiform cartilage and the cartilages of the six lower ribs. 



a. The crura arise by tendinous fibres aggregated into two bundles, 

 fi-om the first, second, and third lumbar A^ertebra^, and the interposed 

 fibro-cartilages on the right side, and from the first and second ver- 

 tebra on the left side. The tendons of both crura curve forwards 

 and upwards so as to enclose the aorta in an arch between them and 

 the bodies of the vertebrte ; their inner margins are united behind, so 

 that they form a nearly complete fibrous ring or oval loop round that 

 vessel. The muscular fibres of the crura, springing from those tendons 

 in thick bundles, on each side of the aorta, diverge as they pass upwards 

 to the central aponeurosis. The innermost fibres on each side decussate 

 with those of the side opposite, those of the right usually lying anterior 

 to those of the left, and, curving upwards, limit an opening for the 

 transmission of the oesophagus, before ending in the central apo- 

 neurosis. 



Fig. 221. — The Lower Half op 

 THE Thorax, with four Lum- 

 bar YERTEBRiE, SHOWIKQ THE 



Diaphragm from before (modi- 

 fied from Luschka). (A. T.) \ 



a, sixth dorsal vei-tebra ; h, 

 fourth lumbar vertebra ; c, ensi 

 form process of the sternum ; d, 

 the aorta descending iu front of 

 the lower dorsal vertebraj ; d' , the 

 aorta emerging in the abdomen 

 below the arch formed by the 

 meeting of the pillars of the dia- 

 phragm ; e, the oesophagus de- 

 scending through its aperture in 

 the diaphragm ; /, opening in the 

 tendon of the diaphragm for the 

 inferior vena cava ; 1, central, 2, 

 right, and 3, left division of the 

 trefoil tendon of the diaphragm ; 

 4, right, and 5, left muscular part, 

 descending from the margins of the 

 tendon to be attached to the ribs ; 

 6, the right, and 7, the left crus 

 or pillar of the muscle ; 8, to 8', 

 in the three upper intercostal spaces 

 of the right side the internal 

 layer of intercostal muscles inter- 

 rupted towards the vertebral co- 

 lumn, where in the two upper 

 spaces the external layer, 9, 9, is 

 seen ; 10, 10, on the left side, 

 subcostal muscles. 



Fig. 221. 



I. The lifjamcntum arcuafum internum is a fibrous band which 

 extends from the body to the transverse process of the first lumbar 

 vertebra, and sometimes also to that of the second, and arches over the 

 upper part of the psoas muscle. The Ugamenfum arcuafum cxfernum 

 extends outwards from the transverse process of the first lumbar 



