The Origin and Development of the Lymphatic System. 5 



organs of absorption for the body, and the physiological theories of 

 filtration. 



Fig. 1. — Diagram to show the " vast serosa " of Boerhave, Haller and 

 others. The veins are striped, the lymphatics are dotted, and the " vasa 

 serosa " which connect them are cross-hatched. The connective tissue is 

 indicated by lines. 



The doctrine, or as His (44) terms it, " the dogma of lymphatics 

 with open mouths," was first combated by a definite counter theory 

 by Schwann (139), following his discovery of the cell in the animal 

 body. The theory of Schwann and notably of Yirchow (150) was that 

 in place of vasa serosa and hypothetical connections which did not 

 exist hollow connective tissue cells spanned the gaps between blood 

 vessels and lymphatics, fig. 2. 



Fig. 2. — Diagram to show the theory of Schwann and of Virchow that 

 the blood vessels are connected with lymphatics by hollow connective tissue 

 cells. The veins are striped, the lymphatics dotted and the hypothetical 

 lymph vessels are cross-hatched. The nuclei denote the fact that cells have 

 been discovered. 



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