98 Mammalia. 



CIECULATOEY SYSTEM Geneeal. 



Absorbent Glands are mucli more numerous in Mammalia 

 tlian in any other class ; but are usually less numerous and 

 more blended together in other orders than in Bimana ; they 

 present themselves on the lymphatics as well as on the 

 lac teals ; those on the lac teals (* mesenteric ') sometimes 

 cluster together into a single mass, named the Pancreas 

 Asellii, at the root of the Mesentery. In the Mam- 

 malia alone of all Yertebrata are conglomerated or 

 conglobate glands met with in the Mesentery. The Lacteals 

 all discharge their contents into a Receptaculum Chylij which 

 is situated in the Lumbar region close to the spine, at which 

 point the superficial l^nnphatics of the lower limbs communi- 

 cate with them. One, or sometimes two, Thoracic ducts are 

 continued anteriorly from the E-eceptaculum, and terminate at 

 the junction of the Jugular and Subclayian Yeins. When 

 the Thoracic duct is single, it is always on the left ; it often 

 resembles rather a plexus of vessels than a single tube ; 

 branches proceeding from it and then re-uniting again ; when 

 there are two ducts, that on the right usually joins its fellow 

 on the left prior to joining the venous system. In some of 

 the lower Mammalia, however, a double thoracic duct is con- 

 stant, one terminating on the left, the other on the right. 

 JS^o rhythmically pulsating sacs have been detected in the 

 absorbent system of Mammalia. When a distinct waU can 



