LYMPHATIC SYSTEM. 135 



is always smaller in its middle than at its beginning, as is seen 

 in Plate II. Sometimes its lower part at m is still larger in 

 proportion than is there represented, and that enlargement has 

 been called the receptaculum chyli, and is considerable in some 

 quadrupeds, in turtle, and in fish : but many anatomists have 

 denied that there is any part of the thoracic duct in the human 

 subject; that deserves the name of receptaculum, and my ex- 

 perience makes me subscribe to their opinion, as I have never 

 seen anything like a pyriform bag, as it has been described, 

 but merely an enlargement not unlike a varix, and that only 

 in few subjects : for commonly it appears, as in this plate, only 

 a little larger than at its middle. This lower extremity of the 

 thoracic duct is formed by the union of two, three, or four 

 very large trunks of lymphatic vessels : these large vessels unite 

 so as to form the duct about the lower part of the first, or the 

 upper part of the second vertebra lumborum, reckoning down- 

 wards. 



These large lymphatic trunks which form the thoracic duct 

 are spread out upon the spine, those of the right side lying 

 below the right cms diaphragrnatis, and 'those of the left pass- 

 ing between the aorta and the spine; whilst the thoracic duct 

 itself lies on the right side of the aorta, between that artery 

 and the right cms diaphragmatis, and behind the emulgent 

 artery of the right side, as is seen in Plate II at n. From 

 this part it passes upwards, being at first covered by the cms 

 diaphragmatis, and afterwards appears at o in the thorax, 

 upon the spine between the aorta and the vena azygos. In the 

 thorax it receives some lymphatics from the intercostal spaces ; 

 a few of which are seen at p and afterwards it receives vessels 

 from the lungs. 



The lymphatics of the lungs are in two sets, one of which 

 passes on the posterior part of each lobe by its root, into the 

 thoracic duct near the middle of the thorax; and another set 

 passes from the fore part of each lobe up towards the jugular 

 and subclavian veins. Some of the lymphatics on the posterior 

 part of the left lobe pass under the aorta to get to the thoracic 

 duct. 



At the root of the lungs, where the large blood-vessels enter, 

 are many glands called bronchial, they are generally of a black- 

 ish colour in the human subject, and have been suspected to 



