NORMAL HISTOLOGY. 



cavities, as the peritoneal or pleural sacs, are, in principle, but 



greatly-dilated lymph-spaces, lined by Fi{ , 



modified connective-tissue cells, the en- 



dothelial plates, which by mutual press- //->/> ,'1 



ure become polygonal in outline ; in- 



FIG. 136. 



Lymph-spaces of cornea, surface view : a, 

 the spaces within the ground-substance (c) con- 

 nected by the minute canals (/>), or canaliculi. 



Lymph - capillary from 

 silver-stained mesentery of 

 frog : a number of lymph- 

 corpuscles occupy the deli- 

 cate endothelial tube which 

 constitutes the vessel. 



FIG. 138. 



stead of a few cells sufficing for the formation of a lining membrane, 



as in the case of the minute 

 lymph-space, innumerable ele- 

 ments are required to clothe 

 the large serous cavity. 



The lymphatic spaces within 

 the connective tissue join to 

 form definite channels at the 

 margins of the fibrous tissue, 

 the lymph being carried by the 

 lymphatic vessels from the 

 organs to the adjacent masses 

 of adenoid tissue, the lym- 

 phatic glands. The lymph- 

 vessels immediately succeed- 

 ing the spaces may be regarded 

 as the lymphatic capil- 

 laries, being protoplasmic 

 tubes of great delicacy, com- 

 posed of a single layer of en- 

 dothelial plates. 



The contours of the lym- 

 phatic vessels are not uniform, but present numerous dilatations and 

 constrictions, which indicate the positions of the imperfect valves : 



Lymphatics of silvered diaphragm of rabbit : s, s, 

 lymph-spaces lying within the deeply-siained ground- 

 substance ; /, /, lymphatic vessels lined with endo- 

 thelium and possessing valves (v) and corresponding 

 dilatations. 



