NERVES OF THORAX AND ABDOMEN. 629 



called a superior vena azygos, which empties into the left 

 vena innominata, and connects also with the lesser azygos. 

 The vena azygos also receives the bronchial, cesophageal, 

 and mediastinal veins. 



The inferior or ascending cava (Fig. 9) returns all the 

 blood of the body from below the diaphragm. The two 

 primitive or common iliac veins, formed by the junction of 

 the external and internal iliacs at the sacro-iliac articula- 

 tion, converge upon the right side, and unite upon th& 

 ligament between the fourth and fifth lumbar vertebrae to 

 constitute the commencement of the ascending cava. 



This great vein now ascends upon the right side and 

 partly in front of the spinal column, on the right psoas 

 muscle, and right crus of the diaphragm, havinsj the aorta 

 upon the left enters the fissure in the posterior part of the 

 liver, and ascends through the tendinous opening in the 

 diaphragm, to which it strongly adheres, to terminate in 

 the inferior and back part of the right auricle. In its 

 course it receives the lumbar, renal, spermatic, phrenic, and 

 hepatic veins. 



The veins of the stomach, pancreas, spleen, and intes- 

 tines, go to form the great portal vein, which is described 

 under the head of the vascular tissue. 



NERVES OF THE THORAX AND ABDOMEN. 



These nerves comprise the sympathetic, the thoracic 

 spinal, the lumbar spinal, pneumogastric, and phrenic. 



The sympathetic in the chest (Fig. 155) consists of twelve 

 dorsal ganglia with their several branches. The ganglia 

 are situated upon the heads of the ribs, covered by the 

 pleura costalis and a thin fascia. Their form is triangular 

 and flat, the apex external, and the base, looking to the 

 spine. They are small, and present the usual gray color 

 and pearl v lustre of the rest of the ganglia composing *the 

 sympathetic system. They are connected above and below 

 to each other by branches called superior and inferior. The 

 other branches are external and internal. 



The external branches, two and sometimes more, or onlj 



