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THE (ESOPHAGUS, OR GULLET. 



powerfully to contract, and by that contraction tlie bolus is forced on until 

 it reaches the gullet, •which is the termination of the pharynx. Before, 

 however, the food proceeds so far, it has to pass over the entrance into the 

 windpipe, and should any portion of it enter that tube, much inconveni- 

 ence and danger might result ; therefore, this opening is not only lined by 

 muscles Avhich close it at the pleasure of the animal, but is likewise covered 

 by a heart-like elastic cartilage, the epiglottis, with its back towards the 

 pharynx, and its hollow towards the aperture. The epiglottis yields to the 

 pressure of the bolus passing over it, and lying flat over the opening into 

 the windpipe, prevents the possibility of anything entering into it. No 

 sooner, however, has the food passed over it, than it rises again by its 

 own elasticity, and leaves the upper part of the windpipe once more open 

 for the purpose of breathing. 



THE (ESOPHAGUS, OR GULLET. 

 The oesophagus consists of a muscular membranous tube extending from 

 the pharynx to the stomach, and conveys the food from the mouth to the 

 stomach. At the top of the neck, it is immediately behind the windpipe, 

 but it soon inclines to the left, and runs down the neck close to the wind- 

 pipe, and on its left. Having entered the chest between the first two ribs, 

 the gullet passes along the upper part of it, and then piercing the dia- 

 phragm, or midriff, enters the stomach. It is composed of three coats ; 

 the outer one of slight loose cellular substance : the middle one muscular, 

 and divided into two distinct layers, the outermost layers having the fibres 

 lengthways, by which the gullet may be shortened, and in shortening 

 widened for the reception of the food ; — the fibres of the inner layers run- 

 ning circularly round the tube, so that the portion immediately above a 

 pellet of food will by its contraction force the food downward, and by 

 successive actions drive it into the stomach. The inner coat, which is a 

 continuation of the membrane of the pharynx, lies in folds or plaits, ex- 

 tending lengthways. The muscular coat, being highly elastic, readily 

 gives way to the pressure of the food, and these plaits enable the inner or 

 cuticular coat, likewise, sufficiently to dilate. 



The oesophagus does not, however, enter straight into the stomach, and 

 with a large open orifice ; but there is an admirable provision made to 

 prevent the regurgitation of the food when the stomach is filled and the 

 horse suddenly called upon to perform unusually hard work. The oeso- 

 phagus enters the stomach in a somewhat curved direction, — it runs 

 obliquely through the muscular and cuticular coats for some distance, and 



then its fibres arrange themselves 

 around the opening into the 

 stomach. Close observation has 

 shown that they form themselves 

 into segments of cii^cles, interlacing 

 each other, and by their conti-action 

 plainly and foi'cibly closing the 

 opening, so that the regurgitation 

 of the food is almost impossible. 



The annexed diagram by Mr. 

 Ferguson, of Dublin, will give a 

 general idea of the structure of 

 the termination of the oesophagus, 

 and the manner in Avhich it en- 

 circles the orifice of the stomach. 

 A mici'oscope of very feeble power will beautifully show this sin- 

 gular constriiction. It is not precisely either a sphincter muscle or 



