Chap, xi.] THE LYMPHATIC VESSELS. 85 



exceedingly thin connective tissue membrane with a 

 few elastic fibres. The valves are semi-lunar folds of 

 the endothelium and intima-. 



111. The lymphatics in the tissues and organs 

 form rich plexuses. They are tubular vessels, the wall 

 of which is, like that of a capillary blood-vessel, a single 

 layer of endothelial plates (Fig. 52). The lymphatic 

 may be, and often is, many times wider than a blood 

 capillary. The endothelial plates are elongated, but 



;U\IB 



Fig. 52. Lymphatic Vessels of the Diaphragm of the Dog, stained with 

 Nitrate of Silver. 



The endothelium forming the wall of the lymphatics is well shown ; v, valves. 

 (Atlas.) 



not so long as in a blood capillary, with more or less 

 sinuous outlines, but this depends on the amount of 

 shrinking of the tissue in which the vessel is embedded ; 

 when there is no shrinking in the tissue or in the vessel, 

 the outlines of the cells are more or less straight. 



The lymphatics are supported by the fibrous con- 

 nective tissue of the surrounding tissue, which does 

 not, however, form part of their wall. 



