150 



DISEASES OF THE (ESOPHAGUS. 



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. 



Localised attacks of oesophagitis, accidental injuries and fissuring of 

 the oesophageal muscular tissue, produced by clumsy efforts to displace 

 foreign bodies with the probang, are the principal 

 causes of dilatation. When the probang is impru- 

 dently or clumsily manipulated, it may press exces- 

 sively at any point where the oesophagus makes a 

 slight bend, and thus split the contracted muscular 

 coat without injuring the lax mucous membrane. 



Oesophageal 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 

 excentric pressure. 



Symptoms. When the dilatation develops 

 slowly and progressively, as a consequence of mus- 

 cular 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 care- 

 fully 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. 



J 



Fig. 66. — Schema of 

 oesophageal stricture 

 (the muscular layer 

 above the stricture 

 has undergone atro- 

 phy ; the mucous 

 membrane is di- 

 lated). 



