THORACIC DUCTS. 



come gray, and finally black, following in these respects the 

 change of colour in the lungs. According to Mr. Pearson, 

 their complexion depends upon the deposite of pure carbon. 



In pulmonary consumption these glands are always enlarged, 

 and look scrofulous. 



SECT. VIII. OP THE THORACIC DUCTS. 



The Left Thoracic Duct (Ductus Thoracicus Sinister) is the 

 main stream of the absorbent system to which almost all the 

 others are but tributary, and by divers routes ultimately find 

 their way into it. It begins about the second or third lumbar 

 vertebra, in front of its body. Shortly after its commencement, 

 while still in the abdomen, it suffers a dilatation more or less 

 considerable, and varying in its shape in different subjects. 

 This is called the Reservoir of Pecquet, or the Receptaculum 

 Chyli; the dilatation, however, is frequently absent, and does 

 not seem to be an essential part of the structure : in our pre- 

 parations at the University some have it, and others have it 

 not. 



The thoracic duct enters the thorax between the crura of the 

 diaphragm, to the right of, and behind the aorta ; it then ascends 

 on the front of the dorsal vertebra, between the aorta and the 

 vena azygos, in front of the right intercostal arteries, and be- 

 hind the oesophagus. At the fourth dorsal vertebra it begins 

 to incline in its ascent to the left side, and then ascends into 

 the neck near the head of the first rib ; it rises commonly as 

 high up as the upper margin of the seventh cervical vertebra; 

 it then turns downwards and forwards, over the left subclavian 

 artery within the scaleni muscles, and, finally, discharges into 

 the angle of junction of the left subclavian and internal jugular 

 vein. 



The preceding is the most simple, and perhaps the most com- 

 mon form, under which the thoracic duct is presented, but va- 

 rieties are continually occurring in its place and mode of origin, 

 in its trunk, and its manner and place of termination. It com- 

 monly begins by the union of three absorbent trunks ; one for 

 each side of the pelvis, along with the corresponding lower ex- 

 tremity; and a middle one for the chyliferous vessels, which 



