THE (ESOPHAGUS 231 



the diaphragm, and the fibres which surround it have a 

 sphincteric action. 



In the abdomen, the oesophagus bends to the left to join the 

 cardiac end of the stomach. This part of the tube is only half an 

 inch in length, but, partly owing to the bend which it makes to 

 the left and partly owing to the sphincteric action of the oeso- 

 phageal opening in the diaphragm, it may hinder the operation 

 of gastroscopy by obstructing the passage of the instrument. 



(Esophageal Obstruction. The thoracic portion of the 

 oesophagus may be compressed by aneurisms of the aortic 

 arch (p. 319), by mediastinal tumours, originating either in 

 the thymus or in the lymph glands, or by abscesses in con- 

 nexion with the upper thoracic vertebrae. Such abscesses 

 cause obstruction by compressing the oesophagus against the 

 unyielding aorta and left bronchus. 



Malignant stricture affects the oesophagus at the three points 

 where it normally shows a slight degree of constriction. These 

 occur (i) At the commencement of the tube, or 6 inches 

 from the incisor teeth ; (2) at the point where the oesophagus 

 is crossed by the left bronchus, or 10 inches from the incisor 

 teeth; and (3) at the distal end of the tube, or 15 inches 

 from the incisor teeth. (Esophageal bougies should be 

 graduated in such a way that the operator can locate the site 

 of the stricture. Before such an instrument is passed, the 

 possibility that the obstruction is due to an aneurism of the 

 aortic arch must be carefully excluded. It should also be 

 remembered that a carcinomatous stricture may be very friable, 

 and it is then readily perforated by a bougie. A little difficulty is 

 often experienced in guiding the instrument past the prominent 

 upper border of the lamina (posterior arch) of the cricoid 

 cartilage, and care must be taken not to diagnose a stricture 

 at this point without sufficient evidence. 



In all muscular tubes the stage of hypertrophy on the 

 proximal side of an obstruction is followed, sooner or later, by 

 a stage of dilatation. On this account, when the site of an 

 oesophageal obstruction is placed low down in the thorax, 



