396 THORACIC DUCT. 



mesenteric, and those of the descending colon and rectum to the lum- 

 bar glands. 



The Lymplmiic vessels of the kidney follow the direction of the blood- 

 vessels to the lumbar glands situated around the aorta and inferior 

 vena cava; those of the supra- renal capsules, which are very large and 

 numerous, terminate in the renal lymphatics. 



The Lymphatic vessels of the viscera of the pelvis terminate in the 

 sacral and lumbar glands. 



The Lymphatic vessels of the testicle take the course of the spermatic 

 cord in which they are of large size ; they terminate in the lumbar 

 glands. 



THORACIC DUCT. 



The thoracic duct* commences in the abdomen, by a considerable 

 and somewhat triangular dilatation, the receptaculum chyli, which is 

 situated upon the front of the body of the second lumbar vertebra, 

 behind and between the aorta and inferior vena cava, and close 

 to the tendon of the right cms of the diaphragm. From the upper 

 part of the receptaculum chyli the thoracic duct ascends through the 

 aortic opening of the diaphragm, and along the front of the ver- 

 tebral column, lying between the thoracic aorta and vena azygos, to 

 the fourth dorsal vertebra. It then inclines to the left side, passes 

 behind the arch of the aorta, and ascends by the side of the oesophagus 

 and behind the perpendicular portion of the left subclavian artery 

 to the root of the neck opposite the seventh cervical vertebra, where 

 it makes a sudden curve forwards and downwards, and terminates 

 at the point of junction of the left subclavian with the left internal 

 jugular vein. 



The thoracic duct is equal in size to the diameter of a goose- 

 quill at its commencement from the receptaculum chyli, diminishes 

 considerably in diameter towards the middle of the posterior me- 

 diastinum, and again becomes dilated near its termination. At 

 about the middle of its course it frequently divides into two branches 

 of equal size, which reunite after a short course ; and sometimes 

 it gives off several branches, which assume a plexiform arrangement 

 in this situation. Occasionally the thoracic duct bifurcates at the 

 upper part of the thorax into two branches, one of which opens 

 into the point of junction between the right subclavian and jugu- 

 lar veins, while the other proceeds to the normal termination of 

 the duct on the left side. In rare instances the duct has been 

 found to terminate in the vena azygos, which is its normal desti- 

 nation in some Mammalia. 



The thoracic duct presents fewer valves in its course than lym- 



* The thoracic duct was discovered by Eustachius, in 1563, in the horse : he 

 regarded it as a vein, and called it the vena alba thpracis. The lacteals were 

 first seen by Asellius in 1622, in the dog; and within the next ten years by 

 Veslingius in man. 



