RELATION OF LYMPHATIC TO BLOOD- VASCULAR SYSTEM 13 



in the course of a detailed joint investigation of the development 

 of these organs. We consequently failed to correctly recognize 

 the origin of the adult lymphatico-venous junctions, and regarded 

 them as direct secondary connections of the systemic lymphatics 

 with the veins. The paper quoted, however, describes the 

 genesis of the lymphatic vessels in their relation to the venous 

 system correctly. 



VI. In 1907 I published, 22 based on McClure's and my own 

 joint investigations, a genetic interpretation of the development 

 of the mammalian lymphatic system as a whole, in which I defined 

 the same as the product of the union of two genetically different 

 and very unequal portions: 



1. The entire extensive system of the lymphatic vessels 

 proper of the adult animal, including the thoracic and right 

 lymphatic ducts and their tributaries, is formed by the confluence 

 of extra-venous intercellular mesodermal spaces, in the sense 

 above defined (V). 



These spaces are lined by a lymphatic vascular endothelium 

 which is not derived from the haemal vascular endothelium, but 

 develops independently of the same. The lymphatic channels, 

 which result from the confluence of these spaces, follow in large 

 part the embryonic veins closely, but they are neither derived 

 from them, nor do they communicate with them, except at 

 definite points, at which the rudimentary mammalian type of 

 lymphatico-venous heart is developed. 



2. A definite structure, the Jugular Lymph Sac, develops 

 in the prevalent and typical mammalian lymphatic organization, 

 directly from a perivenous capillary reticulum of the early pre- 

 and postcardinal veins, adjacent to and including their point of 

 confluence to form the duct of Cuvier. This jugular lymph sac, 

 or rudimentary homologue of one of the lymph hearts of lower 

 vertebrates, arising directly from the veins, subsequently separ- 

 ates for a short period entirely from the same, and finally makes 

 two sets of permanent connections: 



22 G. S. Huntington: "The Genetic Interpretation of the Development of the 

 Mammalian Lymphatic System." Anat. Record, vol. ii, 1908, pp. 19-45. 



