366 OPEEATIONS ON THE DIGESTIVE APPARATUS. 



and veins, which cross its course and fiirther back, returning be- 

 tween the trachea and the longus colli, it passes over the left bron- 

 chia and to the right of the thoracic aorta. Beyond this, placed 

 between the folds of the posterior mediastinum, it is received 

 iato the groove of the iatemal face of the lungs, with the oesoph- 

 ageal arteries and nerves. Passing through the opening of the 

 right pillar of the diaphragm, we find it in its abdomiaal portion 

 related on the right to a notch of the superior border of the hver, 

 and ending at the cardiac. The structure of the cBsophagus is 

 formed of two coats ; one of external and muscular, the other 

 of internal and mucous membrane. The external is composed 

 of muscular fibers, spiral, red and longitudinal, striated ia 

 its anterior three quarters, and white in the posterior quarter. 

 Anteriorly, the crico-pharyngeus furnishes it with a sort of circu- 

 lar necktie. Towards its posterior portion, the muscular coat is 

 much thicker than in the other parts, and as it passes through the 

 pillars of the diaphragm, it is more or less pressed upon. These 

 three points must be remembered, inasmuch as they serve to ex- 

 plain the resistance which is encountered by instruments, such 

 as the catheter, or the probang, when introduced into its cavity. 

 The internal coat or mucous membrane is whitish, vrith longi- 

 tudinal folds, which are so developed at the cardia that they may 

 resist the passage of the probang into the stomach. 



CESOPHAGEAL CaTHETEEISM 



is an operation consisting in the introduction of a special instru- 

 ment, sohd or hoUow, but always flexible, into the cavity of the 

 oesophagus, either to remove bodies that obstruct it, or to aid the 

 exit of gases which have accumulated in the stomach. 



It is therefore indicated in three principal conditions, viz.: 

 first, tympanitis in ruminants; second, in cases of oesophageal 

 dilatation, or jabot ; and third, to dislodge foreign bodies arrested 

 in its canal. 



In cases of tympanitis, it is of advantage if the trouble is not 

 too far developed, and danger of suffocation not too imminent. 

 In cases of oesophageal jabot, due to a more or less extensive 

 dilatation of the organ, in consequence of the lodgment and 

 packing of food, it is in many instances of but very little benefit. 

 "When foreign bodies are lodged in the oesophagus, an accident 

 to which horses are liable, and which is very common in cattle 



