38 ANATOMY OF THE LYMPHATIC SYSTEM. 



the lymph-sac, and the lumen is thereby partitioned into a number of 

 spaces. While at one point this proliferation occurs sparingly, at a 

 neighbouring point the lumen of the lymphatic-sac may be quite 

 free, or these branched cells may be so plentiful as to form a tolerably 

 close network, which differs from a young adenoid reticulum only in 

 respect of the somewhat greater amount of protoplasm which occurs 

 round the nuclei at the nodes of the network. From what has been 

 said, only this conclusion can be drawn, that the growth of a network 

 of branched cells proceeds from the endothelium of the lymphatic sac, 

 whereby the lymphatic vessel is transformed into a cavernous or 

 sinuous structure. It is very easy to make out at all points and in all 

 'stages of development, with great clearness, that not only from the 

 endothelium of the wall of the lymphatic vessel, but also from the 

 branched cells extending across its lumen, lymph corpuscles origi- 

 nate, which become finally detached and lie in the meshes of the reti- 

 culum, or in fact in the lumen of the previous lymphatic vessel. In 

 a completely formed nodule of this sort, which we designate as endo- 

 lymphangial nodules, one cannot of course any longer determine its 

 origin ; all that one sees is a delicate reticulum, with lymphoid cells in 

 its meshes, and supplied with a more or less rich capillary network. 

 For the same reason, also, in the case of a fully develop ed nodule or cord 

 of the first form, i.e. a peri-lymphangial nodule or cord, which owes 

 its origin to an aggregation of lymph-canalicular cells, it is not easy 

 to distinguish it from an endo-lymphangial noduleor cord, inasmuch as, 

 as we have already mentioned above, the at first more or less flat cells 

 gradually transform into an adenoid reticulum, in the meshes of which 

 lymphoid corpuscles lie, while at the same time the fibrillar ground- 

 substance disappears. We wish to add here, for the better understand- 

 ing, two other points, namely, 1. That those lymphatic nodules and 

 cords which are surrounded by a distinct semicircular lymphatic 

 vessel, and whose reticulum is continuous with the endothelium of the 

 lymphatic vessel, correspond to a peri-lymphangial nodule ; and 2. 

 That the proliferation of an endo-lymphangial nodule extends more 

 and more into the lymphatic vessel invaginating or accompanying a 

 large blood-vessel, so that, therefore, the large blood-vessel seems to 

 be enclosed in a lymphatic cord. This then comes to resemble 



