DILATATION OF THE (ESOPHAGUS. 151 



At the commencement of the meal the dilatation is usually empty, or 

 nearly empty. A mouthful of food is swallowed. It descends the oeso- 

 phagus until it arrives at the diverticulum, into which it partially or 

 wholly passes, the peristaltic wave of contraction ceasing at this point. 

 The second mouthful follows with the same result, then a third, a fourth, 

 etc. The diverticulum soon becomes filled to repletion, and no more food 

 can enter it. The food therefore accumulates in the upper portion of the 

 cesophageal tube until the latter becomes nearly filled ; but as this tube, 

 provided its innervation is intact, is intolerant of the presence of any 

 foreign body, and as efforts to swallow prove fruitless, a sudden anti- 

 peristaltic wave of contraction occurs, with the result that all the material 

 contained in the tube above the dilatation is ejected into the mouth, 

 whence it falls into the manger. The same result follows any further 

 attempts to swallow during a particular feeding time. From this it will 

 be seen that the animal can ingest at a given time only as much as the 

 dilatation will contain. 



In the intervals between meal times and under the action of the saliva 

 and warmth, the food collected in the dilatation becomes softened, breaks 

 down, and slowly moves onw^ard towards the rumen. When the next 

 feeding time arrives the dilatation is almost empty, and the same set of 

 symptoms recurs. 



If, instead of forage, the animal begins by taking gruel or very fluid 

 material, deglutition appears normal, or at least fairly easy ; but if drinking 

 is deferred until after taking hard food, it becomes almost impossible, 

 because the passage is obstructed. These symptoms are, so to speak, 

 pathognomonic. Under any circumstances they are so significant that 

 error in diagnosis is unlikely. 



By careful examination oesophageal regurgitation can very easily be 

 distinguished from true vomiting ; the character of the rejected material 

 shows that it has not come from the stomach, while the boluses of food 

 ^ preserve their cylindrical form, and are still saturated with saliva. 



Some secondary signs also deserve to be mentioned, such as the 

 animal's anxiety and restlessness whilst its neighbours are feeding, the 

 existence of trifling and intermittent tympanites due to suppressed 

 iructation, suppression or irregularity of rumination, constipation, etc. 

 it a later stage there is rapid wasting and disordered appetite, and 

 'finally the patients die slowly of hunger, whatever efforts are made to 

 feed them. 



When the seat of dilatation is in the cervical portion of the oesophagus, 

 there are other symptoms which leave no doubt as to the condition. 

 When empty the pouch cannot be detected ; but during a meal the accu- 

 mulation of food causes it to assume the appearance of a doughy, diffuse, 

 indolent swelling, w^hich alters the outline of the jugular furrow, yields 



