CH. XVIII.] 



LYMPHATICS. 



225 



namely (c) in blind dilated extremities in the villi of the small 

 intestine. (See fig. 38, p. 29.) 



Structure of Lymph Capillaries. The structure of lymphatic 

 capillaries is very similar to that of blood-capillaries ; their walls 

 consist of a single layer of elongated endothelial cells with 

 sinuous outline, which cohere along their edges to form a delicate 

 membrane. They differ from blood-capillaries mainly in their 



fig. 230. Lymphatics of central tendon of rabbit's diaphragm, stained with silver nitrate. 

 The shaded background is composed of bundles of white fibres, between which the 

 lymphatics lie. /, Lymphatics lined by long narrow endothelial cells, and showing t> 

 valves at frequent intervals. (Schofield.) 



larger and very variable calibre, and in their numerous communi- 

 cations with the spaces of the lymph-canalicular system. 



In certain parts of the body, stomata exist, by which lymphatic 

 capillaries directly communicate with parts formerly supposed to 

 be closed cavities. They have been found in the pleura, and in 

 other serous membranes ; a serous cavity thus 'forms a large 

 lymph-sinus or widening out of the lymph-capillary system with 

 which it directly communicates. 



A very typical plexus of lymphatic capillaries is seen in the 

 central tendon of the diaphragm. Fig. 230 represents the appear- 

 ance presented after staining with silver nitrate. 



K.P. 



