ANATOMY IX A NUTSHELL. 



immediately above the liver. This is a litth higher than the left side. The 

 lowest part of it is the righl crus which reaches in the fourth lumbar vertebra. 

 The under surface is cov< red with p( ritone um. 1 1 is One of the so-called double 

 Ik Ui< (I musch s. 1 1 has its origin in frorrt from th< < asiform cartilage, from the 

 sides, from the under surfaces of the cartilages and bony portion of the six or 

 seven lower ribs interdigitating with the Transversalis muscle, also from the 

 two aponeurotic arches called the ligamentum arcuatum externum el internum. 

 The last one is the covering of the Psoas magnus, the first one is the covering of 

 the Quadratus lumborum. Behind ii is connected to the spine by two crura 

 or legs, the right one is the longer i xtending from the anterior surface of the 

 bodi< s and intervertebral substance of the thrc e or four upp< r lumbar vertebrae; 

 tin left one from the anterior surfaces of th< two upper ones. From this origin it 

 - to the central or cordiform tendon which consists of three leaflets, the 

 righl one is the largest, the left on< the smallest, and the middle one is inter- 

 im diate in size. On each sid( of tin ensiform attachment tin re is a weak place 

 which may be brok< n; th< n we nay have what is called a phrenic or diaphrag- 

 matic hernia. Some of the contents of the abdomen protrude into the chest, 

 or ptts in the mediastinum may descend through it into the abdominal cavity. 

 The diaphragm has three large and several small natural foramina. The one 

 mosl posterior is really not in the diaphragm bui between the two crura which 

 arc joined posteriorly by a tendinous band. This is called the aortic opening, 

 and transmits the aorta, vena azygos major, the thoracic duct, and sometimes 

 the left sympathetic nerve; when this nerve does not pass through this open- 

 ing it goes through the left crus. The vena azygos major occasionally goes 

 through the right crus. The second large opening is in front, and a little to the 

 left of the aortic opening; it transmits the oesophagus and the pneumogastric 

 oerves. Th< left pneumogastric passes in front of the oesophagus. The right 

 one, which passes b; hind it, goes into the solar plexus, which is situated behind 

 the stomach. The third large opening is farther in front than the others and 

 lies in the c< ntral tendon. Ii is son u what quadrilateral in form and is called 

 the foramen quadratum; the inf< rior v< na cava passes through it. 



The smaller openings are through the crura. Those in the right crus transmit 

 the great* r and less* r splanchnics and the sympathetic nerves of the right side, 

 occasionally the vena azygos major. The left cms transmit the vena azygos 

 minor, the greater or lesser splanchnic nerves of the left side and the sympathe- 

 tic nerve of the left side when it does not pass through the aortic opening. The 

 blood supply of the diaphragm is derived from the two phrenic, the internal 

 mammary, and the lower intercostal arteries. The phrenic arteries are two 

 small arteries which may arise separately from the aorta above the coeliac axis. 

 < hien .me is derived from the aorta and the other from the renal arteries. They 

 very rarely arise as two separate vessels from the aorta. The nerve supply is 

 the phrenic which comes from the third, fourth, and fifth cervical nerves. The 

 phrenic plexus also helps to supply it. This plexus is made by the phrenic 

 nerve and branches from the semilunar ganglion of the solar plexus. The 

 laity call the diaphragm the midriff, which comes from the Saxon words which 

 mean the middle of the belly. The solar plexus or abdominal brain and the 



