484 LYMPH-CAPILLARIES. [BOOK n. 



The lacteal radicle of a villus ( 262) is such a lymph- 

 capillary, more or less tubular in form, or perhaps club-shaped 

 and sometimes bifurcate or branched, placed by itself in the midst 

 of the reticular tissue of the villus, ending, or as we should perhaps 

 say beginning, blindly near the apex of the villus and joining 

 below by a valvular mouth a regular lymphatic canal forming part 

 of the network of regular lymphatic vessels with which as well as 

 with lymph-capillaries the connective tissue of the mucous mem- 

 brane is furnished. 



In other parts of the body where connective tissue runs, 

 lymph-capillaries are more or less abundant, all passing their 

 contents on to the more regular lymphatic canals. In certain 

 parts, as for instance in the central nervous system, the smaller 

 blood vessels are surrounded by large lymph-capillaries, or by 

 regular lymphatic vessels, in the shape of tubular sheaths. In 

 these cases the lymph-capillary forms a sort of hollow jacket 

 around the artery or vein which, covered with a layer of sinuous 

 epithelioid plates, lies in the middle of a tubular space lined with 

 similar sinuous plates. The plasma which exudes through the 

 walls of the blood vessel passes accordingly at once into the 

 tubular space or interior of the lymph-capillary, whence it is 

 earned away into the regular lymphatic canals. Such an arrange- 

 ment is spoken of as a " perivascular lymphatic." 



288. The lymph-capillaries may in one sense be regarded 

 as the beginnings of the lymphatic system ; they are the first 

 lymphatic passages definitely lined with a continuous epithelium. 

 But lymph exists outside these capillaries. In treating of connec- 

 tive tissue 105 we more than once spoke of the spaces between 

 the interlacing bundles of fibrillae as lymph-spaces ; and indeed 

 they are during life occupied by fluid, which may be spoken of as 

 lymph. It is fluid which has in some way or other passed into 

 them from the blood stream, through the walls of the capillaries 

 and other minute blood vessels. We shall speak of this passage as 

 a process of transudation and shall consider its nature later on. 

 Many of the larger of these spaces, the areolae of areplar connec- 

 tive tissue, are completely lined by epithelioid plates with sinuous 

 outlines; these are in fact lymph-capillaries. But many spaces, 

 especially the smaller ones, are not so lined ; these lie outside 

 the lymph-capillaries. Nevertheless they contain lymph, which 

 reaching them by transudation through the walls of the blood 

 vessels, streams from them in some way or other into the lymph- 

 capillaries and so into the other lymphatic vessels. Coloured 

 fluid injected by means of a fine syringe into these spaces soon 

 finds its way into the lymphatics; and besides, in the vast majority 

 of cases, a certain number of these spaces always intervene between 

 the wall of the capillary or other small blood vessel from whence 

 the lymph comes and the lymph-capillary to which the lymph 

 goes ; the lymph must have some means or other of passing from 



