LYMPHATIC AND LACTEAL SYSTEM. 



225 



Fig. 53. 



Sk. X x. 



The thoracic duct and ritjlit lymphatic trunk, 

 ( After Mascagni ) 



a, Thoracic duct. 



b, The right lymphatic trunk. 



c, The trunk of the cervical lymphatics entering 



separately the internal jugular vein. 

 s, Subclavian vein. 

 .;, Internal jugular vein. 

 x, Vena azygos. 



tinum, having the aorta to its left, the vena 

 azygos to its right, and the oesophagus 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 

 cervical 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 forwards and outwards, then down- 

 wards 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. III. 



The principal irregularities in the arrange- 

 ment of the thoracic duct, which have been 

 recorded by anatomists, are a double 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 leftside, 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 sca'.enus 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 ard 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 

 lymphatics 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 



