THE DIGESTIVE SYSTEM 



175 



soon pass by transformation into other forms, and become 

 assimilated to the pre-existing elements of the circulating 

 fluid. In this way they accomplish, finally, the object of 

 digestion, and replenish the blood by a supply of new 

 material from without. 



THE THORACIC DUCT 



The thoracic duct begins in the abdomen by a consider- 

 able dilatation which is situated in front of the lower 



Longus colli 

 muscle. 



Esophagus 



Vertebral vein. 

 FIG. 89. Topography of the thoracic duct (Zuckerkandl). 



portion of the spinal column. From this point it passes 



