THE DIAPHRAGM. 



245 



Fig. 196. 



arched and converging manner to be inserted into the anterior and external 

 margins of the central tendon. 



d. The central tendon trefoil or cordiform tendon, or phrenic centre, 

 is a strong aponeurosis, forming the central and highest part of the 

 diaphragm. It is elongated from side to side, and consists of three lobes or 

 alee, partly separated by indentations. The right lobe is the largest ; and 

 the left, which is elongated and narrow, is the smallest of the three. The 

 central tendon is surrounded on every side by the muscular portion of the 

 diaphragm, the fibres of which are directly continuous with those of the 

 tendon. The tendinous fibres cross one another, and are interwoven in 

 various directions. 



Fig. 196. VIEW OP THE 

 DIAPHRAGM, FKOM BE- 

 LOW. I 



In the preparation from 

 which this figure is drawn, 

 the lower ribs and sternum 

 are thrown upwards so as 

 to expose and stretch the 

 lower surface of the dia- 

 phragm, and the four 

 tipper lumbar vertebrae 

 have been exposed by the 

 removal of all the muscles 

 on the right side, and the 

 dissection of the psoas mag- 

 nus and quadratus lumbo- 

 rum on the left side, a, 

 the aorta emerging in the 

 abdomen below the ten- 

 dinous arch formed by the 

 union of the pillars of the 

 diaphragm on the first 

 lumbar vertebra ; b, the 

 oesophagus seen entering 

 the abdomen through the 

 aperture in the united 

 muscular crura (this aper- 

 ture should have been 

 represented a little to the 

 left of the middle line) ; 

 c, the aperture for the 

 vena cava inferior situated 

 at the place of union of 

 the middle and right divi- 

 sions of the trefoil tendon ; d, the body of the fourth lumbar vertebra ; e, e, the twelfth 

 ribs near their extremities ; /, /, the ends of the eleventh ribs ; 1, the tendinous part 

 of the right crus ; 2, the left ; 3, the tendinous arch formed by their union over the 

 aorta, above which the decussation of muscular fibres is seen ; 4, second decussation of 

 muscular fibres in front of the cesophageal opening ; 5, on the right side, placed near the 

 end of the transverse process of the first lumbar vertebra, towards which, arching from 

 above and from within, over the + , is seen the ligamentum arcuatum internum ; and 

 from which, passing towards e, is seen the ligamentum arcuatum externum ; 5', on the 

 left side, is in a similar position, but here the quadratus lumborum muscle is seen 

 descending from the twelfth rib behind the ligamentum arcuatum externum, and the 

 tipper part of the psoas muscle is within the ligamentum arcuatum internum ; 6, the middle 

 division of the trefoil tendon, from which in front pass the slips of attachment of the 

 diaphragm to the ensiform process ; 7, the left, and 8, the right divisions of the trefoil 

 tendon ; from the outer and anterior margins of these the costal slips of the muscle are 

 seen diverging, and from the posterior border of the tendon the slips of origin proceeding 

 from the ligarnenta arcnata and the tendinous arch of the crura ; 9, part of the quadratus 

 lumborum ; 10, part of the psoas magnus. 



