408 OTTO F. KAMPMEIER 



the azygos veins and derived from them, but he later withdrew 

 this view since it was based on the studjr of an insufficient num- 

 ber of critical stages. 



Concerning all lymphatic vessels, not including the lymph 

 hearts, Huntington 11 maintained the theory advanced jointly 

 by McClure and himself in 1906, that lymphatics have their origin 

 in the fusion of extra-intimal spaces which arise irregularly and 

 disjointly along primitive temporary venous channels. 12 Thus 

 he says: 



The peripheral general lymphatic channels appear to be developed by 

 confluence of spaces independent of the venous system, although closely 

 associated with the same. The histological picture presented by them 

 differs radically from that of the jugular veno-lymphatic derivatives. 

 They begin as minute extravenous vacuoles closely applied to the sur- 

 face of the veins which they accompany. They enlarge as the lumen of 

 the veins diminishes. They become confluent with each other but 

 they never from their first inception contain red blood cells, nor do they, 

 as far as I have been able to ascertain in numerous carefully studied 

 series of excellent preservation.and fixation, communicate with the blood 

 channels. 



In 1908, Sabin published a short paper 13 in which she reviews the 

 several positions held relative to the genesis of lymphatic channels 

 and attempts to turn the evidence in favor of the centrifugal 

 growth theory. Concerning Lewis' multiple anlagen she says: 



Since these spaces are lined with a definite endothelium, they form a 

 much more serious obstacle to the theory of growth of the lymphatics 

 from the endothelium of the veins than the more indefinite spaces to be 

 found in earlier embryos, and I cannot but think that if these multiple 

 endothelial-lined isolated spaces do exist along the veins in the later stages, 

 they would form serious evidence against the theory of the origin of the 

 lymphatics from the veins. Or at least if the lymphatics, in their growth, 

 do pick up isolated endothelial-lined spaces, we shall again be left with- 

 out a clue as to the origin of the lymphatic system. 



11 George S. Huntington: The genetic interpretation of the development of the 

 mammalian lymphatic system. Anat. Rec, vol. 2, 1908, pp. 19-45. 



12 This theory was presented by Huntington and McClure before the Associa- 

 tion of American Anatomists in 1906 and published as a preliminary account in the 

 Anatomical Record no. 3 and in the American Journal of Anatomy, vol. 6, 1907. 



13 Florence R. Sabin : Further evidence on the origin of the lymphatic endo- 

 thelium from the endothelium of the blood vascular system. Anat. Rec, vol. 

 2, 1908, pp. 46-54. 



