490 ABDOMEX. 



The Anterior mediastinum is a triangular space, bounded in front 

 by the sternum, and on each side by the pleura. It contains a quan- 

 tity of loose cellular tissue, in which are found some lymphatic 

 glands and vessels passing upwards from the liver; the remains of 

 the thymus gland, the origins of the sterno-hyoid, sterno- thyroid, and 

 triangularis sterni muscles, and the internal mammary vessels of the 

 left side. 



The Middle mediastinum contains the heart enclosed in its peri- 

 cardium ; the ascending aorta ; the superior vena cava ; the bifurca- 

 tion of the trachea; the pulmonary arteries and veins; and the 

 phrenic nerves. 



The Posterior mediastinum is bounded behind by the vertebral 

 column, in front by the pericardium, and on each side by the pleura. 

 It contains the descending aorta; the greater and lesser azygos 

 veins, and superior intercostal vein; the thoracic duct; the osso- 

 phagus and pneumogastric nerves ; and the great splanchnic nerves. 



ABDOMEN. 



The abdomen is the inferior cavity of the trunk of the body ; it is 

 hounded in front and at the sides by the lower ribs and abdominal 

 muscles ; behind, by the vertebral column and abdominal muscles ; 

 above, by the diaphragm ; and, below, by the pelvis : and contains 

 the alimentary canal, the organs subservient to digestion, viz. the 

 liver, pancreas, and spleen, and the organs of excretion, the kidneys, 

 with the supra-renal capsules. 



Regions. For convenience of description of the viscera, and for 

 reference to the morbid affections of this cavity, the abdomen is 

 divided into certain districts or regions. Thus, if two transverse 

 lines be carried around the body, the one parallel with the convexi- 

 ties of the ribs, the other with the highest points of the crests of the 

 .ilia, the abdomen will be divided into three zones. Again, if a per- 

 pendicular line be draw r n at each side, from the cartilage of the 

 eighth rib to the middle of Poupart's ligament, the three primary 

 zones will each be subdivided into three compartments or regions, a 

 middle and two lateral. 



The middle region of the upper zone being immediately over the 

 small end of the stomach, is called epigastric (st! yatf<n^, over the 

 stomach). The two lateral regions being under the cartilages of 

 the ribs are called hypochondriac (0*0 xovSgoi, under the cartilages). 

 The middle region of the middle zone is the umbilical; the two 

 lateral, the lumbar. The middle region of the inferior zone is the 

 hypogastric (u*o ya^g, below the stomach) ; and the tw r o lateral, 

 the iliac. In addition to these divisions, w^e constantly use the term 

 inguinal region, in reference to the vicinity of Poupart's ligament. 



Position of the Viscera. In the upper zone will be seen the liver, 

 extending across from the right to the left side ; the stomach and 

 spleen on the left, and the pancreas and duodenum behind. In the 

 middle- zone is the transverse portion of the colon, with the upper 

 part of the ascending and descending colon, omentum, small intes- 

 tines, mesentery, and, behind, the kidneys and supra-renal capsules. 



