LYMPIIATIC AND LACTEAL SYSTEM. 
The thoracic duct and right lymphatic trunk. 
After Mascagni. 
a, Thoracic duct. 1 
b, The right lymphatic trunk. ’ 4 
e, The trunk of the cervical lymphatics entering 
separately the internal jugular vein. 
8, Subclavian vein. 
9, Internal jugular vein. 
_ #, Vena azygos. 
tinum, having the aorta to its left, the vena 
_ azygos to its right, and the esophagus in front. 
In this position it ascends as high as the fourth 
_ or third dorsal vertebra, at which level, con- 
_ tinuing its course upwards, it turns from right 
_ to left, passing behind the descending portion 
_ of the arch of the aorta, above which it ap- 
_ pears a little external to the root of the left 
subclavian artery, from whence continuing to 
ascend it passes between the latter and the 
left common carotid artery, lying on the 
longus colli muscle; it now mounts into the 
tvical region in front of the vertebral artery 
and vein to the level of the seventh cervical 
_ vertebra, opposite to which it begins to form a 
curve, first Aetads and outwards, then down- 
s and inwards, striding over the subclavian 
artery to reach the angle of union between 
_ the subclavian and internal jugular veins, at 
‘which point it empties itself into the venous 
‘system either by one or more branches. 
__ The thoracic duct is not uniform in diameter 
throughout its course ; besides the occasional 
dilatation at its commencement, it generally 
presents another on the fourth dorsal vertebra 
just below its passage behind the descending 
thoracic aorta. Its narrowest part usually cor- 
responds to the sixth or seventh dorsal vertebra. 
The duct is frequently tortuous and rarely 
Single throughout. It often splits into two or 
more branches, which after a longer or shorter 
course reunite; this division and reunion may 
be two or three times repeated, and it may ul- 
timately terminate by two or three branches 
Instead of one. 
VOL. 111. 
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225 
The principal irregularities in the arrange- 
ment of the thoracic duct, which have been 
recorded by anatomists, are—a doublé@ duct, 
one terminating in the left, the other in the right 
side of the neck ; a bifurcation of the duct at 
a higher or lower level, one branch terminating 
in the angle of union of the subclavian and 
internal jugular veins of the left side, the other 
emptying itself either into the corresponding 
point on the right side or joining the right 
lymphatic trunk, close to its termination; a 
single trunk terminating altogether on the right 
side of the conflux of the internal jugular and 
subclavian veins, in which case a short lym- 
phatic trunk is found on the left side similar 
to that which usually exists on the right, con- 
stituting a partial lateral inversion or trans- 
position confined to the trunks of the lymphatic 
system. 
Besides the lymphatics of the lower extre- 
mities and the lacteals, the thoracic duct re- 
ceives directly or indirectly the lymphatics of 
the remaining abdominal viscera (except a few 
from the right lobe of the liver), those from the 
exterior and interior of the lower half of the 
trunk ; also the lymphatics of the left upper 
extremity, and left side of the head and neck, 
those from the left lung, the left side of the 
heart, and from the exterior and interior of the 
left upper half of the body. 
The right lymphatic trunk nearly equals the 
thoracic duct in diameter; it is, however, not 
more than half an inch in length. Its situation 
is in the neck at the level of the lower edge of 
the seventh cervical vertebra, where it will be 
found lying upon of the subclavian vessels close 
to the inner edge of the scalenus anticus muscle, 
and opposite to the union of the subclavian and 
internal jugular veins, at which point it termi- 
nates in the venous system. 
The right lymphatic trunk receives the lym- 
phatics of the right upper extremity and of the 
right side of the head and neck, those from the 
right lung and right side of the heart, some few 
from the right lobe of the liver, and from the 
exterior and interior of the right upper half of 
the body. 
Some of the principal branches which ordi- 
narily empty themselves into the right lym- 
phatic trunk occasionally terminate separately 
in the internal jugular or subclavian veins close 
to their junction. When these vessels all enter 
the veins separately, then the right lymphatic 
trunk is said to be deficient. 
Having described the position of the trunks 
of the lymphatic system as well as the situa- 
tions of the conglobate glands in the various 
parts of the body, I now proceed to trace the 
vessels themselves. 
I shall commence with the description of the 
yop of the lower extremities, as being 
the most remote from the trunks of the system. 
They are divided, as in all other parts of the 
body, into a superficial and deep-seated set, 
which latter accompany the principal bloodves- 
sels. They are associated successively with the 
digital arteries, the internal, external plantar, 
and dorsal arteries of the foot ; in the leg with 
the anterior, posterior tibial, and fibular vessels, 
q 
