THE DIAPHRAGM. 359 



two aponeurotic arches between the last rib and the spinal column, 

 one being placed over the quadratus lumboruin, and the other over 

 the psoas muscle ; and, lastly, from the lumbar vertebrse by a thick 

 muscular piece or pillar. From this extensive origin the fibres are 



directed inwards, with different degrees of obliquity and length, to insertion of 

 i i -i t_ A t T j -._ j.i. fibres into a 



the central tendon ; but some have a peculiar disposition m the central 



pillars which will be afterwards noted. tendon. 



The abdominal surface is concave, and is covered for the most Parts in 

 part by the peritoneum. In contact with it on the right side are the the under 

 liver, kidney and supra renal ; and on the opposite side, the stomach, surfa ce, 

 spleen, kidney and supra renal ; in contact also with the pillars are 

 the pancreas and the solar plexus with the semilunar ganglia. The 

 thoracic surface is covered by the pleura of each side and the peri- and with 

 cardium. At the circumference the fleshy processes of origin alternate JtteSSnent 

 with like parts of the transversalis muscle; but a slight interval of border, 

 separates the slip arising from the ensiform process from that attached intervals in 

 to the seventh cartilage, and a second space comes between the fibres 

 from the last rib and the arch over the quadratus lumber um muscle. 

 These apertures mark the situation between the three parts of which Apertures, 

 the diaphragm is essentially formed, viz., sternal, from the ensiform 

 cartilage, costal, from the costal cartilages, and vertebral, from the 

 vertebrse and the tendinous arch over the psoas muscle. The 

 interval between the vertebral and costal parts near the last rib is 

 occasionally large, and through it a communication between the 

 abdominal and thoracic cavities may take place and abdominal 

 viscera be found in the thorax. 



Structure. The muscle is convex towards the chest, and concave Vault: 

 to the abdomen. Its vault reaches higher on the right than the left 

 side, and is constantly varying during life in respiration. In the 

 condition of rest, as met with after death (state of expiration), the extent up- 

 central portion is about opposite the xiphi-sternal articulation ; on W! s * 

 the right side it rises to the level of the fifth, and on the left side to 

 the sixth chondro- sternal articulation. 



Special parts of the diaphragm. The following named parts are Special 

 now to be noticed more fully, viz., the central tendon, the pillars, examined, 

 the arches, and the apertures. 



The central tendon (cordiform tendon) occupies the middle of the Central 

 diaphragm (fig. 137), and is surrounded by muscular fibres : the 

 large vena cava pierces it. It is of a pearly white colour, and its 

 tendinous fibres cross in different directions. In form it is compared 

 to a trefoil leaf ; of its three lobes or segments the right (c) is the like a trefoil 

 largest, and the left (a) the smallest. 



The pillars (crura) are two large muscular and tendinous processes Two pillars, 

 (d and e\ one on each side of the abdominal aorta. They are narrow 

 and tendinous below, where they are attached to the upper lumbar with arch 

 vertebrae, but large and fleshy above ; and between them is a tendinous m 

 arch over the aorta. 



In each pillar the fleshy fibres pass upwards and forwards, diverging arrangement 

 from each other ; the greater number join the central tendon without each 



