(ESOPHAGUS. 



759 



nerally exist in the human subject. The co- 

 lour of the muscular fibres is pale red, less 

 pale than those of the succeeding portions of 

 the alimentary canal, and less deeply co- 

 loured than those of the pharynx. A micro- 

 scopic examination shews them to be com- 

 posed of both striped and unstriped fibres, 

 mingled to an uncertain extent. " In some 

 specimens from the human subject we have 

 failed in detecting any striped fibres in the 

 lower half of the oesophagus, either in the 

 circular or longitudinal layer ; but in other 

 examples we have found them to within an 

 inch of the stomach."* 



Mucous membrane. The mucous membrane 

 of the oesophagus is of a pale colour ; it pre- 

 sents a number of longitudinal furrows, which 

 are produced by a slight folding of the mem- 

 brane during the partial contraction or ordi- 

 nary tonicity of the circular muscular fibres : 

 the apparent laxity of the mucous membrane 

 is no more than sufficient to allow of the dila- 

 tation of the canal which occurs during the 

 process of deglutition. In addition to the 

 longitudinal furrows there are some finer lines 

 or wrinklings passing in various and indefinite 

 directions, which are analogous to the fine 

 grooved lines observed in the skin of various 

 parts of the body. The mucous membrane is 

 remarkable for its thickness; the epithelium is 

 so abundant as to be distinctly visible to the 

 naked eye ; it forms a thick layer similar to a 

 cuticle, and terminates at the cardiac orifice 

 of the stomach in a well-defined irregular 

 fringed border. It is composed of the lamel- 

 liform or scaly variety of epithelium.f The 

 mucous membrane is connected with the sub- 

 jacent muscular layer by the intervention of an 

 abundant lax areolar tissue, which allows of 

 a movement of these membranes upon each 

 other during the repeated variations to which 

 the diameter of the oesophagus is subject in the 

 process of deglutition. 



(Esophageal glands. In thesubmucous areo- 

 lar tissue of the oesophagus are found a number 

 of small glands. They may be felt through the 

 mucous membrane, which they elevate here 

 and there, as little circular or oval flattened 

 granular bodies ; they are most numerous at 

 the lower extremity of the tube. Their struc- 

 ture is the same as that of the buccal and duo- 

 denal glands. From the duct, which opens 

 on the free surface of the mucous membrane, 

 a few ramifications proceed and become em- 

 bedded in the submucous areolar tissue. The 

 branches are short and sacculated, having the 

 appearance of small vesicles collected on a 

 common stalk. The epithelium lining these 

 glands is of the spheroidal variety .J 



Vessels and nerves. The arteries distributed 

 to the resophagus are derived from several 

 sources. In the neck they come from the in- 

 ferior thyroid artery ; in the chest some come 

 directly from the aorta, others from the inter- 

 costals, and occasionally some from the internal 



* Physiological Anatomy and Physiology of 

 Man, by Todd and Bowman. 



t See the article MUCOUS MEMBRANE. 

 I * Ibid. 



mammary arteries; in the abdomen, branches 

 are derived from the coronaria ventriculi and 

 from the phrenic arteries. The veins corre- 

 sponding to these arteries empty themselves 

 into the inferior thyroid, the superior cava, the 

 azygos, internal mammary, coronaria ventriculi, 

 and phrenic veins. The lymphatics open into 

 the glands which surround the oesophagus in 

 considerable numbers. The nerves are derived 

 chiefly from the pneumo-gastric. The recur- 

 rent branch of the pneumo-gastnc in its course 

 upwards sends numerous filaments to the oeso- 

 phagus. In the chest, as the trunks of the 

 pneumo-gastric nerves lie on the oesophagus, 

 each one sends off filaments which pass 

 backwards, encircling the tube, and meeting 

 with branches from the opposite nerve. The 

 plexus thus formed is called the plexus gulae ; 

 it is joined by some filaments from the thoracic 

 ganglia of the sympathetic. 



Function. The office of the oesophagus is 

 to receive the aliment from the pharynx and to 

 convey it into the stomach. This, the third and 

 last stage of the process of deglutition, is un- 

 attended by sensation and uninfluenced by vo- 

 lition. The following is the mode in which 

 the food is transmitted along the oesophagus. 

 After being duly masticated and moistened in 

 the mouth, it is received into the pharynx, and 

 is thence propelled into the upper orifice of 

 the oesophagus. The muscular fibres, both cir- 

 cular and longitudinal, of that part of the tube 

 into which the food is propelled are at once 

 stimulated to contract ; the mass is conse- 

 quently pushed onwards into the relaxed por- 

 tion of the tube immediately succeeding ; the 

 stimulus of contact with this part produces the 

 same effect upon it as has already been pro- 

 duced upoiwhat part of the tube which the 

 food has just quitted, and the contraction of 

 the first portion continuing at the time when 

 that of the second portion is taking place, the 

 substance is necessarily propelled onwards: it 

 thus comes into contact with successive portions 

 of the tube, and in each successive portion the 

 same effect is produced, the contact of the sub- 

 stance exciting contraction, and the remaining 

 contraction of the part which it has just quitted 

 preventing regurgitation. These phenomena 

 occur in a much less space of time than is 

 occupied in their description, and the food is 

 rapidly transmitted along the entire length of 

 the canal. A notion may be formed of the 

 rapidity with which these contractions are trans- 

 mitted along the oesophagus by observing the 

 rapid vibrating movements in the neck of a 

 horse while drinking. The secretion constantly 

 poured out by the cesophageal glands has the 

 effect of moistening and lubricating the interior 

 of the tube, and thereby of facilitating the 

 transmission of solid portions of food. The 

 contractions of the oesophagus, which ordinarily 

 commence at its pharyngeal and terminate at 

 its cardiac extremity, sometimes take place in 

 a reverse order, the direction of the movement 

 depending on the part to which the stimulus is 

 first applied. Dyspeptic persons are not un- 

 commonly troubled with eructations of a liquid 

 from the stomach, giving rise to what is faiui- 



