[Saccular initial segments of the lymphatic vessel system]

It is commonly said that the lymphatic system begins "blindly" as saccular outpocketings. In order to examine these saccular outpocketings, 120 injections into the conjunctival lymphatics of 60 bovine postmortem eyes were carried out, measuring the level of injection pressure and simultaneously documenting the various filling stages photographically. 20 trials were selected for further analysis. We recorded low initial pressures when the tip of the needle was situated close to a larger lymphatic vessel and the coloured solution (1% aqueous Berliner Blue) as possibly applied intravascularly. Higher initial pressures were seen on positioning inside fine networks of vessels. Extremely high initial pressures without any visible filling of vessels but in the presence of simultaneously increasing depots of dye were probably caused by absent or insufficient connection between the tip of the needle and a vessel. During lymphography numerous coarser and finer, tube-like projections (saccular outpocketings) filled, from which further progression of the coloured solution could only be observed when higher injection pressures were applied. We were able to prove that such segments had connections to neighbouring vessels as well as forming plexus of their own. Based on our findings we have reason to doubt the existence of tube-like initial segments in the lymphatic system. Rather in the conjunctiva of the bovine eye this system has the structure of a fine network where tube-like segments can be demonstrated as temporary filling stages.