THE LYMPHATICS AND LYMPHATIC GLANDS. 



103 



we have remaining only the endothelial tube with cells simi- 

 lar to those of the blood-vessels. Here also we still meet 

 with valves and isolated nodal or ampulla-like enlargements. 

 Such vessels remain distinctly demarcated from the immedi- 

 ate neighborhood. The relation of these passages to the 

 blood-vessels varies greatly. For the most part, both vessels 

 simply run alongside of each other. Not unfrequently an 

 arterial branch is accompanied by a pair of lymphatic canals. 

 One may then readily commit an error, namely, the assump- 

 tion that the blood current is invested by a lymphatic. The 

 latter condition does, indeed, actually take place (Fig. 88, c), 

 although rarely, as many assert. 



At last, however, the appearance of the lymphatics changes ; 

 the outer surface of our vascular cells has now grown firmly 

 together with the surrounding tissues ; 

 thus there arises at the first examination 

 the impression of a cavity and cleft. For- 

 merly this was generally considered to be 

 the true interpretation, until the employ- 

 ment of the dilute solution of nitrate of 

 silver opened our eyes (Fig. 98, a). 



For the examination of the finest termi- 

 nal lymphatics, artificial injections are nat- 

 urally again requisite ; and, indeed, to a 

 higher degree than in the capillaries of the 

 blood passages, where under favorable 

 conditions the colored cells permit the fine 

 tubes to stand out. The lymph, a colorless fluid, poor in 

 cells, does not do this, as is known, and only the chyle ves- 

 sels, overladen with fat, become at times distinctly prominent 

 without any further assistance. 



But, as is known, the lymphatics have no affluent tube 

 comparable to an artery ; they show merely a capillary divi- 

 sion and effluent canals, comparable to the veins. Filling 

 the latter downwards is, almost without exception, prevented 

 by the resistance of the valves. A highly celebrated modern 

 anatomist, Hyrtl, rendered the service of discovering a very 



Fig. 98. --Lymphatic ca- 

 nal from the large intestine 

 oi the Guinea-pig; a, vas- 

 cular cells ; 6, spaces be- 

 tween the same. 



