EPITHELIAL AND ENDOTHELIAL TISSUE. 345 



and the above-named observers considered them clefts between the tendinous 

 bundles. On the pleural surface is observed a reticulum of lymphatics, which 

 is blued by injection, the small vessels gradually passing into larger lymph- 

 vessels. The colored liquid has penetrated the lymphatics through openings 

 in the central portion of the peritoneum covering the diaphragm. The 

 stomata present in this situation, and which are surrounded by small globular 

 elements, were termed lymph-wells by Eanvier. 



Dybkowski found similar openings also in the endothelial 

 investment of the parietal pleura ; these openings are confined 

 exclusively to the intercostal spaces, while in the pleura covering 

 the ribs the stomata are absent. By the injection of colored 

 substances into the pleural sac, results are obtained similar 

 to those in the peritoneal cavity. The subjacent lymph- vessels 

 in all these localities are distinctly marked by an endothelium, 

 therefore are not simply interstitial tissue-clefts. The assertion 

 of Von Recklinghausen that the connective tissue is pervaded by 

 spaces and canals, destitute of walls of their own, and thought to 

 be the roots of the lymphatic system, is erroneous, as proved in 

 the chapter on connective tissue. Every space rendered visible 

 by the staining with nitrate of silver contains a bioplasson body 

 demonstrable by staining with chloride of gold. The apparent 

 connections between the " juice-canals " of the connective tissue 

 and the lymph- vessels proper, in specimens stained with nitrate 

 of silver, although rarely seen, are explicable by the fact that 

 neither the bioplasson bodies nor the lymph- vessels take up the 

 silver stain. Observers agree, however, that at the periphery of 

 the connective-tissue corpuscles and of the territories there are 

 narrow spaces containing a liquid ; but we are not justified by 

 any facts in connecting these spaces with the lymphatic system. 



Lymph-ganglia and Lymph-tissue. These are peculiar forma- 

 tions of the myxomatous connective tissue, which are closely allied 

 to the lymphatic system. Their characteristic feature is a delicate 

 reticulum, the meshes of which are crowded with lymph-corpus- 

 cles i. e., bioplasson bodies exhibiting all stages of develop- 

 ment, from a small, homogeneous granule to a nucleated plastid, 

 similar to the colorless blood-corpuscle (see page 105 and Fig. 

 31). This tissue is widely spread throughout the submucous 

 layers, and reaches its highest development in the youngest 

 individuals. It is arranged in conglomerated heaps the so-called 

 lymph-follicles in the tonsils, the pharynx, the base of the 

 tongue, the wall of the stomach, the submucous layer of the 

 intestines, in the lymph-ganglia, along the lymph-vessels in 



