906 aii | THE VASCULAR SYSTEM. 
Occasionally the thoracic duct commences and terminates in the usual manner, but crosses 
the vertebral column immediately after its origin and ascends on the left side. 
: Not uncommonly there is no distinct receptaculum chyli, in which case the terminal 
lymphatic vessels of the abdomen merely unite to form a larger vessel which does not present 
any obvious dilatation, and from which the thoracic duct is continued. The terminal lymphatic 
q trunk may open into the internal jugular vein previous to its junction with the subclavian, 
instead of into the commencement of the innominate vein. 5 
Occasionally the thoracic duct is double, either on the whole or in part of its extent, and 
sometimes it breaks up into a plexus of vessels which may reunite into a single trunk in the 
upper part of the thorax. Both the thoracic duct and the right lymphatic duct may before 
terminating divide into branches which, though sometimes reuniting on each side into a single 
trunk, not ‘infrequently open separately into the great veins at the root of the neck. 
As a rule the thoracic duct j joins the commencement of the left innominate vein, but it may 
" end in the internal jugular, vertebral, or subclavian veins of the left side; whilst very rarely, it 
opens into the vena azygos major. 
