488 LYMPHATICS OF THE LOWER LIMB. 



aorta ; it then ascends on the right side of that vessel, in contact with the 

 right crus of the diaphragm, to the thorax, where it is placed at first upon 

 the front of the dorsal vertebrae, between the aorta and the azygos vein. 

 The duct ascends, gradually inclining to the left, and at the same time dimi- 

 nishing slightly in size, until it reaches the third dorsal vertebra, where, 

 passing behind the arch of the aorta, it comes into contact with the oeso- 

 phagus, lying between the left side of that tube and the pleura. Con- 

 tinuing its course into the neck to the level of the upper border of the 

 seventh cervical vertebra, it changes its direction and turns forwards, at the 

 same time arching downwards and outwards so as to describe a curve over 

 the apex of the pleura, and then terminates on the outer side of the internal 

 jugular vein, in the angle formed by the union of that vein with the sub- 

 clavian. The diminution in the size of the duct as it ascends is such that 

 at the fifth dorsal vertebra it is often only two lines in diameter, but above 

 this point it again enlarges. The duct is generally waving and tortuous in 

 its course, and is constricted at intervals so as to give it a varicose ap- 

 pearance. 



The thoracic duct is not always a single trunk throughout its whole extent ; it 

 frequently divides opposite the seventh or eighth dorsal vertebra into two trunks, 

 which soon join again ; sometimes it separates for a short distance into three divisions, 

 which afterwards unite, and enclose between them spaces or islets. Cruikshank in 

 one case found the duct double in its entire length ; " in another triple, or nearly so." 

 In the neck, the thoracic duct often divides into two or three branches, which in some 

 instances terminate separately in the great veins, but in other cases unite first into a 

 common trunk. In a case of right aortic arch the thoracic duct has been observed to 

 end in the veins of the right side (A. Thomson). 



The thoracic duct has numerous double valves at intervals throughout 

 its whole course, which are placed opposite to the nodulated parts of the 

 vessel. They are more numerous in the upper part of the duct. At the 

 termination of the duct in the veins there is a valve of two segments, so 

 placed as to allow the contents of the duct freely to pass into the veins, 

 but which would effectually prevent the reflux of either chyle or blood into 

 the duct. 



THE RIGHT LYMPHATIC DUCT. 



The right lymphatic duct is a short vessel, about a line or a little more 

 in diameter, and about a quarter or half an inch in length, which receives 

 the lymph from the absorbents of the right upper limb, the right side of 

 the head and neck, the right side of the chest, the right lung, and the right 

 half of the heart, and from part of the upper surface of the liver. It 

 enters obliquely into the receding angle formed by the union of the right 

 subclavian and internal jugular veins, where its orifice is guarded by a double 

 valve. 



LYMPHATICS OF THE LOWER LIMB 



AND SURFACE OF THE LOWER HALF OF THE TRUNK. 



The lymphatics of the lower limb are arranged in a superficial and a deep 

 series. Those of the superficial series, together with the superficial lym- 

 phatics of the lower half of the trunk, converge to the superficial inguinal 

 glands ; with the exception of a few which dip into the popliteal space. 

 Those of the deep series converge to the deep inguinal glands. 



