78 Florence R. Sabin. 



brought out especially in a study of the lymphatic system in reptiles 

 (57). After a confused account of the origin of the anterior lymph 

 hearts he describes the development of the peripheral lymph vessels 

 out of tissue spaces. He says that whereas in mammals the greater 

 number of the lymphatic vessels come from extra-intimal spaces (57, 

 p. 272) in reptiles, on the other hand, the lymphatics come from 

 tissue spaces without relation to the veins. 



The theory that in the pathway of developing lymphatic vessels 

 certain tissue spaces enlarge and are added onto the growing tips 

 has been worked out by two pupils of McClure, Kampmeier (66a) and 

 Stromsen (146a), both of whom published their work in 1912. 



Kampmeier's first article (66) is a preliminary report of the second 

 (66a). He has worked on the development of the thoracic duct in the 

 pig and bases most of his conclusions on a reconstruction of a speci- 

 men of mine. Kampmeier thinks that the thoracic duct develops in 

 an anterior-posterior direction by the addition of certain connective 

 tissue spaces which enlarge in the pathway of a developing vessel. 

 This is a return to the view of the earlier embryologists, except that 

 they believed that the growth was from the periphery toward the center. 



To a certain extent Kampmeier still holds to the theory of lym- 

 phatics from extra-intimal spaces; that is, he believes that a part of 

 the thoracic duct follows veins that are degenerating. A vein which 

 lies in the pathway of a developing lymphatic vessel he calls a " veno- 

 lymphatic." This is a different use of the term from that of Hunting- 

 ton and (McClure, who used the term to mean a vein which was trans- 

 formed into a lymphatic vessel. This latter use of the term can well 

 be given up, since veins do not become lymphatics. The replacing 

 of degenerating veins Kampmeier does not regard as a fundamental 

 process in the development of lymphatics, since they may or may not 

 follow such veins. He thinks. that in the development of the thoracic 

 duct about half the duct comes from extra-intimal spaces (66a, p. 

 434). It is interesting to note in connection with the degeneration 

 of veins in Kampmeier's work that he speaks of the plexus of veins 

 medial to the nervous sympatheticus, fig. 11 (or fig. 11 in 66a), as 

 veno-lymphatics; that is, as veins which disappear as the thoracic 

 diict forms, and yet this same plexus of veins can be readily injected 

 in embryo pigs 27 to 30 mm. long; stages in which the thoracic duct 

 is well formed. It is true that the blood vessels may not show in 

 uninfected specimens, just as the plexus of blood capillaries around 



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