At the commencement of the meal the dilatation is usually empty, or nearly empty. A mouthful of food is swallowed. It descends the œsophagus 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 œsophageal 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 antiperistaltic 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 onward 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 œsophageal 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 eructation, suppression or irregularity of rumination, constipation, etc. At 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.