42 



CLASSIFICATION 



colourless fluid, consisting of plasma and colourless corpuscles. 

 It is contained in the large internal cavities of the body, in 

 minute crevices which exist in the substance of the various 

 organs, and in delicate lymphatic vessels which ramify in most 



Fig. 18.— The Thoracic Duct and Lymphatic Vessels. 312, The duct, opeiang into great veins at 3. 



parts of the body. Those of the intestines are termed lacteals, 

 and receive the digested fats. Most of the lymphatics ulti- 

 mately open into the thoracic duct (fig. i8), a narrow tube 

 lying ventral to the backbone, and opening on the left-hand side 

 into the great veins at the base of the neck. In this way the 

 blood receives the digested fats, and a constant supply of 

 colourless corpuscles. 



