232 THE DIGESTIVE SYSTEM 



food is retained for some time before it is ejected, and there 

 may be some doubt as to whether or not it has been within 

 the stomach. The mucous membrane of the oesophagus 

 contains numerous mucous glands, and, consequently, ejecta 

 from the oesophagus are alkaline in reaction and are mixed 

 with mucus. In all doubtful cases, the diagnosis can be made 

 clear by examination with the fluorescent screen during the 

 passage of a bismuth meal. 



In order to examine the oesophagus with X-rays, the patient is 

 placed obliquely with reference to the screen, so that the shadow 

 of the bismuth may be seen satisfactorily, as it passes down in 

 front of the vertebral column and behind the pericardium. 



The arteries of the oesophagus are derived, in the neck, from 

 the inferior thyreoids : in the thorax, from the descending 

 thoracic aorta : in the abdomen, from the left gastric (coronary) 

 artery. They anastomose freely with one another, and similar 

 communications exist between the veins, which join the vena 

 azygos in the thorax and the left gastric vein in the abdomen. 

 In this way the systemic and portal circulations are connected 

 with one another, and, in portal obstruction, this venous 

 anastomosis may become greatly enlarged in the lax sub- 

 mucous tissue of the oesophagus. The rupture of varicose 

 veins in this situation gives rise to haematemesis, which may 

 be the first sign of cirrhosis of the liver (p. 274). 



The nerves of the oesophagus are derived from both vagi, 

 which form a plexus on its walls in the thorax (p. 100). This 

 plexus is reinforced by fibres from the sympathetic trunks, and 

 their centres in the spinal medulla are situated in the upper 

 thoracic segments. Pain referred from the oesophagus is 

 usually experienced over the lower part of the sternum, in 

 the areas supplied by the terminal branches of the fourth 

 and fifth intercostal nerves. It is most marked when violent 

 peristaltic movements affect the circular muscular fibres on the 

 proximal side of an obstruction, 



