86 ELEMENTS OF HISTOLOGY. [Chap. xi. 



112. The outline of the vessel is not straight, but 

 more or less moniliform, owing to the slight dilatations 

 present below and at the semi-lunar valves ; these are 

 folds of the endothelial wall, and they are met with in 

 great numbers. The vessel appears slightly dilated 

 immediately beyond the valve, that is, on the side 

 farthest from the periphery, or rootlet, whence the 

 current of lymph starts. 



113. Tracing the lymphatic vessels in the tissues 

 and organs towards their rootlets, we come to more or 

 less irregular-shaped vessels, the wall of which also 

 consists of a single layer of polygonal endothelial plates j 

 the outlines are very sinuous. These are the lym- 

 phatic capillaries; in some places they are mere clefts 

 and irregular sinuses, in others they have more the 

 character of a tube, but in all instances they have 

 a complete endothelial lining, and no valves. 



Sometimes a blood-vessel, generally arterial, is 

 ensheathed for a shorter or longer distance in a 

 lymphatic tube, which has the character of a lym- 

 phatic capillary ; these are the perivascular lymphatics 

 of His, Strieker, and others. 



114. The rootlets of the lymphatics are situ- 

 ated in the connective tissue of the different organs 

 in the shape of an intercommunicating system of 

 crevices, clefts, spaces, or canals, existing between the 

 bundles, or groups of bundles, of the connective tissue. 

 These rootlets are generally without a complete endo- 

 thelial lining, but are identical with the spaces in 

 which the connective tissue corpuscles are situated ; 

 where these are branched cells anastomosing by their 

 processes into a network such as the cornea, or serous 

 membranes we find that the rootlets of the lymphatics 

 are the lacunae and canaliculi of these cells the typical 

 lymph-canalicular system of von Recklinghausen. (Fig. 

 53). The endothelial cells forming the wall of the 

 lymphatic capillaries are directly continuous with the 



