(SOPHAGUS. 
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 csophagus, 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 esophagus 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 
“nase of deglutition. In addition to the 
ngitudinal 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 
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 toa 
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.t The 
mucous membrane is connected with the sub- 
_ jacent muscular layer by the intervention of an 
_ abundant lax areolar tissue, which allows of 
_amovement of these membranes upon each 
_ other during the repeated variations to which 
_ the diameter of the cesophagus is subject in the 
| process of deglutition. 
_ Csophageal.glands.—In the submucous areo- 
lar tissue of the esophagus are found a number 
of small glands. They may be felt through the 
(nracons membrane, which they elevate here 
ty 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- 
\ ed 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.{ 
_ Vessels and nerves.—The arteries distributed 
to the @sophagus 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. 
| + See the article Mucous MEMBRANE. 
|. ¢.lbid, 
759 
Mammary arteries; in the abdomen, branches 
are derived from the coronaria ventriculi and 
from the phrenic arteries. The veins corre- 
sponding to these arteriés_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 csophagus in 
considerable numbers. The nerves are derived 
chiefly from the pneumo-gastric. The recur- 
rent branch of the pneumo-gastric in its course 
upwards sends numerous filaments to the cso- 
phagus. In the chest, as the trunks of the 
pneumo-gastric nerves lie on the cesophagus, 
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 gule ; 
it is joined by some filaments from the thoracic 
ganglia of the sympathetic. 
Function—The office of the esophagus 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 cesophagus. 
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 ceesophagus. 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 upon that 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 esophagus by observing the 
rapid vibrating movements in the neck of a 
horse while drinking. The secretion constantly 
poured out by the esophageal 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 cesophagus, 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 fami- 
