302 THE LYMPHATIC SYSTEM, BY F. v. RECKLINGHAUSEN. 



recognise, from the position of these processes, what direction 

 the lymph current pursues in any particular vessel, since they 

 are so arranged that, like the valves of the larger lymph 

 vessels, they prevent any regurgitation of the fluid. 



The arrangement of the capillary lymphatics in reference to 

 the bloodvessels is a subject of special interest. The larger 

 lymphatics run sometimes in immediate proximity to the 

 arteries and veins, and sometimes separately, or, at all events, 

 present no constant relation to them. But for the smaller and 

 capillary lymphatics, the general statement may be made that 

 they hold their course at as great a distance as possible from 

 the blood capillaries. This characteristic feature may be most 

 easily recognised in membranous expansions, in which the blood 

 and lymphatic capillaries are distributed upon one plane : in 

 such cases the points of junction of the lymphatic plexus al- 

 ways occupy the middle points of the meshes of the blood 

 capillaries, and the converse. It is evident that this arrange- 

 ment is most advantageous for the purpose of drainage. All 

 fluid escaping from the blood capillaries must traverse the 

 tisssue to reach the capillaries ; and so long as this transudation 

 occurs, a continuous play of fluid around all the tissues must 

 take place. If, on the other hand, the lymphatic efferent canals 

 lay in immediate contiguity to the blood capillaries ; if the 

 whole were not, so to speak, intercalated between the tubes of 

 the lymphatic system and of the bloodvessels, the fluids 

 might easily stagnate in those parts which were more remote 

 from both, and a constant interchange of material would cease 

 to take place. There is yet another point that is deserving of 

 notice. In those membranes which present a free surface 

 covered with an epithelium, as in the mucous and serous mem- 

 branes and the skin, the lymph capillaries are found constantly 

 to occupy a deeper plane than the bloodvessels. Whilst the 

 latter ascend till they lie just beneath the epithelium, the 

 lymphatic capillaries do not reach the uppermost stratum of 

 connective tissue. These relations are most easily recognised 

 in the membrane forming the web of the foot in the Frog, 

 which is a duplication of the external skin ; the lymphatics 

 here exclusively lie in the middle connective tissue layer, 

 whilst the bloodvessels course in the thin cutaneous laminae 



