414 DISEASES OF THE PHARYNX AND (ESOPHAGUS. 



animals, it will be considered separately in each. The obstructing 

 bodies are divisible into two classes : — (a) Wound-producing foreign 

 bodies which pierce the mucous membrane, and remain in position in 

 consequence of their rough surface ; and (6) mere mechanical obstruc- 

 tions which, on account of their size, are unable to pass through the 

 tube. The first are most frequently found in the pharynx, the second 

 in the oesophagus, though the first are also met with in the gullet. 



According to Rubeli's experiments, the striped muscular fibres, which 

 in man are confined to the first two-thirds of the oesophagus, are in animals 

 continued almost to the stomach. In ruminants the oesophagus possesses 

 no unstriped muscular tissue whatever. This first appears in the rumen. 

 In all animals the mucous membrane is invested with a thick stratified 

 epithelium, covered with numerous papillae, and the mucosa possesses 

 lymph follicles together with mucous glands. The area of the oesophageal 

 tube stands in inverse proportion to the strength of its muscular coat. 

 In the region of the cardiac opening a thickening or narrowing occurs 

 in all domesticated animals with the exception of cattle and dogs. 



The oesophagus of the horse is absolutely and relatively the longest, 

 but also the narrowest. According to Franck, its length is from 49 to 

 65 inches. Rubeli found it to be from 50 to 52 inches, measured in position, 

 and in larger animals even 56 to 70 inches. Its walls are strong, and 

 become so much thicker between the diaphragm and the cardiac opening 

 that the lumen of the tube almost entirely disappears, explaining the 

 frequent occurrence in this region of diverticula, stenoses, and obstructions. 



The oesophagus of ruminants and carnivora is more cylindrical. In 

 oxen a contraction occurs at the lower end of the upper third, and from 

 this point onwards the diameter increases, while the wall is comparatively 

 thin, and decreases in strength from above downwards. 



In sheep the thickness increases from below upwards, but the muscular 

 wall is very thin in comparison with the surface of the mucous membrane. 

 The narrowing at the middle of the oesophagus, remarked in the goat, is 

 wanting in the sheep. 



Swine have also a contraction at the middle of the tube, which from 

 this point enlarges both above and below. In dogs the narrowest point 

 lies at the height of the lower portion of the cricoid cartilage, the width 

 being about If inches. The tube increases from here to a circumference 

 of 2£ inches, then narrows to 2 inches, dilates for a second time, and, about 

 6 inches behind the pharynx, attains a circumference of 3 inches. The 

 last contraction, about 2| inches in front of the cardia, measures 2J inches. 

 From here the oesophagus widens like a funnel, until it enters the stomach 

 (the figures refer to the width of the mucous membrane). 



In cats two contractions exist : the upper lies § inch behind the pharynx, 

 the lower at the point where the oesophagus pierces the diaphragm. 



(a.) FOREIGN BODIES IN THE PHARYNX AND (ESOPHAGUS 

 OF THE HORSE. 



In horses foreign bodies very seldom become fixed in the pharynx, 

 but are more frequent in the oesophagus. As stated, they generally 



