Dilatations are more frequent than strictures. Their mode of origin is easily understood. When the muscular tissue has lost its tonicity and contractile power at a given point, or when, as a consequence of any form of inflammation, it has begun to undergo atrophy, the mucous membrane becomes herniated, because its circumference is not supported regularly during deglutition. The ectasia, which at first is of small size, becomes more marked in consequence of the tendency that exists for the food to accumulate in the dilated region. Dilatation is thus set up. [Illustration: $1] Localised attacks of œsophagitis, accidental injuries and fissuring of the œsophageal muscular tissue, produced by clumsy efforts to displace foreign bodies with the probang, are the principal causes of dilatation. When the probang is imprudently or clumsily manipulated, it may press excessively at any point where the œsophagus makes a slight bend, and thus split the contracted muscular coat without injuring the lax mucous membrane. Œsophageal contractions, as we have seen, may form the point of origin of dilatations, but in this case the dilatations are more regular in form, and affect the entire circumference of the tube. The muscular tissue is still everywhere normal, and becomes dilated in consequence of equally-applied eccentric pressure. =Symptoms.= When the dilatation develops slowly and progressively, as a consequence of muscular atrophy, the symptoms remain unnoticed for a long time, and the owner only begins to be anxious when the animal loses condition, or when the driver or cowman detects masses of half-chewed food mixed with the saliva in the manger. Certain signs are pathognomonic; others may be regarded as of secondary importance. By carefully watching an animal which is feeding the following symptoms may be noted: As a general rule hunger is very marked, and the animal chews its food and swallows the first few mouthfuls in a perfectly normal way. Three, five, eight, or even ten mouthfuls may be swallowed; then the animal suddenly stops, appears a little anxious, extends its head and neck, an antiperistaltic contraction occurs, and one or two masses of food are rejected and fall into the manger. The discomfort being thus momentarily relieved, the animal, which is dying of hunger, although faced with food which it is unable to swallow, returns to its meal, swallows one, two, or three boluses of food, regurgitation again occurs, and the whole process is repeated. What is going on under these circumstances is easy to explain.