12 DEVELOPMENT OF THE SYSTEMIC LYMPHATIC VESSELS 



starting points, the lymph channels of the entire body develop 

 by a process of continuous and uninterrupted centrifugal "sprout- 

 ing" toward the periphery. 16 - 17 ' 18 ' 19 - 20 



V. The systemic lymphatics are formed by confluence of 

 perivenous mesodermal spaces, developed, as separate anlages, 

 outside the intima of the early venous channels, but not communi- 

 cating with the same except at definite points of lymphatico- 

 venous connection which are secondarily formed. 21 



This view pronounces for the ontogenesis of endothelial cells, 

 lining the separate mesodermal spaces, independently of the 

 haemal vascular endothelium. The spaces forming the first 

 anlages of the systemic lymphatic vessels are in no sense derived 

 from the embryonic veins, although closely associated with them 

 topographically. 



At the time of the publication of the paper embodying these 

 views, McClure and I were not aware of the important role 

 played by the jugular lymph sacs, as affording the portals of 

 entry of the entire systemic lymphatic circulation into the 

 venous system. This relation was only subsequently ascertained 



16 F. R. Sabin: "On the Origin of the Lymphatic System from the Veins, and 

 the Development of the Lymph Hearts and Thoracic Duct in the Pig." Am. Jour. 

 Anal., vol. i, 1902, pp. 367-389. "On the Development of the Superficial Lym- 

 phatics in the Skin of the Pig," Am. Jour. Anat., vol. iii, 1904, pp. 183-195. "The 

 Development of the Lymphatic Nodes in the Pig and the Relation to the Lymph 

 Hearts," Am. Jour. Anat., vol. iv, 1905, p. 355-389. "Further Evidence on the 

 Origin of the Lymphatic Endothelium from the Endothelium of the Blood Vascu- 

 lar System," Anat. Record., vol. ii, 1908, pp. 46-54. "The Lymphatic System 

 in Human Embryos, with a Consideration of the Morphology of the System," 

 Am. Jour. Anat., vol. ix, 1909, pp. 43-90. 



17 W. J. MacCallum: "Die Beziehung der Lymphgefasse zum Bindegewebe." 

 Arch. f. Anat. und Phys., Anat. Abth., 1902. 



18 G. Heuer: "The Development of the Lymphatics in the Small Intestine of the 

 Pig." Am. Jour. Anat., vol. ix, no. 1, 1909. 



19 W. A. Baetjer: ''The Origin of the Mesenteric Lymph Sac in the Pig." Anat. 

 Record, vol. ii, 1908. 



20 H. Hoyer, "Untersuchungen iiber das Lymphgefasssystem der Froschlarven. 

 I. Theil." Extrait du Bulletin de I' Academic des Sciences de Cracovie, Clv*s3 des 

 Sciences mathematiques et naturelles. Juillet, 1905. II. Theil, ibid., Mai, 1908. 



11 G. S. Huntington and C. F. W. McClure: "The Development of the Main 

 Lymph Channels of the Cat in their Relation to the Venous System." Am. Jour. 

 Anat., vol. yi, 1907. Abstr. Anat. Rec., vol. i, pp. 36-41. 



