THE LYMPHATIC VESSELS OF THE SEROUS MKMIJUANES. :J.J 



Hum distinctly coloured ; in the tube lies the blood-vessel, the wall of 

 which shows the spindle-shaped endothelium on its inner surface. 



In this case, where the lymphatic appears, not, as in the common 

 silver preparations, in the form of a clear space showing endothelial 

 markings on a dark ground, but as a wide tube, there is hardly any 

 possible room for mistake, inasmuch as one can see, even with a low 

 power, that the blood-vessel is contained, as if it were a thin rod, 

 within the wide tube. In the first case, also, where the lymphatic 

 shows itself as a clear space with endothelial markings, a mistake will 

 not readily be made if one has before him an invagination extending 

 over a long tract ; for in that case it can be seen that the lymphatic 

 makes certain bends, which affect both sides of it together that is, 

 the impression on one side of the vessel has its corresponding and 

 complementary deflection on the other. The importance of this as 

 a criterion will appear from the following considerations. The blood- 

 vessel lying in a lymphatic has that surface which is directed towards 

 the lumen of the lymphatic also covered by an endothelium. There 

 appears, therefore, in the optical longitudinaL^ection on each side of 

 the vessel, an endothelial membrane, i.e. a membrane with oblong- 

 nuclei disposed at regular intervals the endothelium being seen of 

 course in profile. It presents, therefore, the appearance as if a lym- 

 phatic ran on each side of the vessel. In this manner the above- 

 mentioned condition, viz. that the bendings of the lymphatic on both 

 sides of the blood-vessel correspond to and complement each other, 

 is of importance for deciding whether we have before us one lymphatic 

 in which the blood-vessel is invaginated, or a pair of lymphatics. 



The lymphatics are also to be seen in the fresh omentum, provided 

 that the part is mounted in serum and has not been subjected to any 

 mechanical injury. After having studied the lymphatics in well- 

 silvered preparations, both those accompanying the blood-vessels as 

 well as the invaginating variety of them, one may recognise them 

 also in fresh objects. They present themselves as broad tracts which 

 appear to be bounded by a membrane with oblong nuclei disposed at 

 regular intervals ; that is, one sees the endothelial membrane in 

 profile. 



