990 THE DIGESTIVE SYSTEM. 
below this the cesophagus is crossed by the left bronchus (Fig. 666, C), and in 
the rest of its thoracic course it les in the closest relation to the back of the 
pericardium. Sehind, it rests on the longus colli muscle and the vertebral column 
in the wpper part of the thorax; but below the bifurcation of the trachea, as 
already explained, it advances into the cavity of the posterior mediastinum, and is 
soon separated from the spine by the vena azygos major, the thoracic duct, and in 
its lower part by the aorta as well. j 
On its left side lie the thoracic duct, the pleura, and the left subclavian artery 
in the upper part of the thorax ; the aorta in the middle region ; and lower down the 
pleura again, for a little way, before the cesophagus pierces the diaphragm. On the 
right side the tube comes into relation with the arch of the azygos vein, whilst 
below this the pleura clothes it. 
The two pneumogastric nerves, after forming the posterior pulmonary plexuses 
behind the roots of the lungs, descend to the cesophagus, where they form, by unit- 
ing with one another and with the branches of the sympathetic, the plexus gule or 
cesophageal plexus. Lower down the left nerve winds round to the front, whilst the 
right turns to the back, and in this relation they pass with the tube through the 
diaphragm to reach the stomach. 
Relation of the Aorta to the Gsophagus.—The arch of the aorta, passing back to reach 
the vertebral column, les in relation to the left side of the cesophagus; consequently the 
descending thoracic aorta lies at first to its left; lower down, however, as the aorta passes on to 
the front of the vertebral column, and the gullet inclines forwards and to the left, the cesophagus 
comes to lie at first in front, and then, as the diaphragm is approached, it les not only in front, 
but also somewhat to the left of the artery (Figs. 665 and 666). 
Relation of the Thoracic Duct to the Gsophagus.—The thoracic duct, lying to the right 
of the aorta below, is not directly related to the cesophagus (Fig. 666, E); but higher up 
(Fig. 666, D and E) it lies behind it. About the level of the aortic arch the duct passes to the left, 
and above this (Fig. 666, B and A) will be found resting against the left side of the cesophagus, 
which it accompanies into the neck. 
Relation of the Pleural Sacs to the Gisophagus.—Above the level of the aortic arch and 
the arch of the vena azygos major, between which the tube descends, the pleuree, though not lying in 
immediate contact with the cesophagus, are separated from it only by a little connective tissue, 
and on the left side also, behind the subclavian artery, by the thoracic duct (Fig. 666, B). Here, 
in thin bodies, the pleura is very close to the ceesophagus, and the thoracic duct, lying on its left 
side, may occasionally be seen through the pleural membrane. Below the arch of the azygos 
vein the pleura clothes the right side of the csophagus—and very often even a considerable 
portion of its posterior surface too, thus forming a deep recess behind it—almost as low down as 
the opening in the diaphragm. On the left side, below the level of the aortic arch, the pleura 
comes in contact with the gullet, only for a short distance, just above the diaphragm (Fig. 666, E). 
Divisions.—Both a diaphragmatic (Jonnesco) and an abdominal part of the a@sophagus are 
described. The diaphragmatic portion, said to be about half an inch in length (1 to 15 cm.), 
corresponds to the portion of the tube which lies in the cesophageal orifice (or canal) of the 
diaphragm. The plane of this orifice is very oblique or almost vertical, and its abdominal 
opening looks forwards and to the left, and but little downwards. Above and in front, where it is 
bounded either by the posterior edge of the central tendon or by a few decussating fibres of the 
muscular portion of the diaphragm, which meet behind the tendon, the cesophageal orifice has 
practically no length, and consequently the cesophagus here passes into the abdominal cavity 
inunediately after leaving the thorax. At the sides and behind, on the other hand, the decus- 
sating bands from the two crura, which embrace the orifice, are so arranged that they turn a flat 
surface (not an edge) towards the opening, and thus, posteriorly and laterally, the orifice or canal 
is of some length; and on these aspects there is a portion of the tube in contact with the 
diaphragm for a distance of 1 to 13cm. But this contact takes place not around a horizontal 
line, but in a very oblique plane corresponding to that of the orifice. ‘On the whole, it is perhaps 
more satisfactory not to describe a separate diaphragmatic portion, but to say that the cesophagus 
pierces the diaphragm very obliquely, and that at the sides and behind it is in contact with the 
walls of the orifice for a distance of half an inch or more. 
The cwsophagus, in passing through the orifice, is connected to its boundaries by a considerable 
amount of strong connective tissue, but it is extremely difficult, or impossible, to demonstrate any 
direct naked-eye connexion between the csophageal muscular fibres and those of the diaphragm. 
The anterior or right boundary of the cesophageal orifice, formed of fibres derived from both 
erura of the diaphragm, is strongly developed and prominent, and usually lies in the esophageal 
groove, on the back of the left lobe of the liver, which groove is rarely due to the pressure of the 
cesophagus alone. 
The abdominal portion of the esophagus is very short, for immediately after piercing the 
diaphragm the tube expands into the stomach. However, when the empty stomach is drawn 
forcibly downwards, a portion of the front and left side of the tube, about half an inch in length 
(1 to 15 cm.), is seen, to which the above term is applied. This part is covered with peritoneum, 
derived from the great sae in front and on the left, whilst its right and posterior surfaces are 
