THE LYMPHATIC VESSELS OF THE SEROUS MEMBRANES. 35 



along the sides of the blood-vessels. For it is easy to understand that 

 this appearance might simply be due to the folded walls of the 

 collapsed lymphatics, and the migratory cells be actually in the lumen 

 of the lymphatics. That there actually occur near the vascular 

 trunks occasional aggregation of lymph-canalicular cells and migratory 

 cells is another and different fact to which we have already directed 

 attention. 



We come now to the important questions Do the lymphatics in 

 the rabbit's omentum form a closed vascular system, or do they take 

 origin among the tissues ? and, In what way do the lymphatics stand 

 related to the above-mentioned patches and cords ? The answer to 

 the first question will become obvious when we have first considered 

 the second question attentively. 



We have already mentioned that in negative-pencilled prepara- 

 tions, as well as in positive, one can convince himself that at certain 

 points the lacunae, or lymph-canalicular cells respectively, are so 

 closely pressed together that they come to be arranged in lines ; that 

 is, they are not united by canals %r processes in their respective cases, 

 but simply joined to one another like the cells of an endothelium. 

 This appearance we shall call that of simple lacunae, understanding 

 thereby the larger lacunae formed by the fusion of a group of lacunar 

 spaces of the lymph-canalicular system, and lined, therefore, on one 

 side with cell-plates arranged like an endothelium. We have already 

 stated, however, that these isolated simple lymph-lacunae are con- 

 nected by means of canals with the isolated lacunae of the adjoining 

 lymph-canalicular system (and the outermost cells, respectively, by 

 processes with the adjoining cells ;) and we shall now add that those 

 simple lymph-lacunae are situated quite superficially that is, under 

 the endothelium of the surface and are but seldom met with in the 

 ground-tissue itself. We may at the same time mention, in connec- 

 tion with those isolated lacunae, also the simple lymph-lacunae that 

 occur in the large-sized patches, concerning which we have already 

 stated that they consist only of an agglomeration of more or less 

 branched cells, with the young cells belonging to them and lying with 

 them in the lymph-canalicular system. In this same kind of patches 

 and cords there is illustrated yet another interesting relation in which 



