VASCULOGENESIS IN THE CAT 9 



bases of the cords, the injection entered in a thin stream for a 

 short distance revealing a cleftlike diminishing lumen. 



Bartels ('09) 4 has given figures which closely correspond to 

 those of MacCallum, but he considers the interpretation of the 

 cell-cords as sprouts debatable. On the other hand, Miss Sabin's 

 figure of lymphatic terminals in a 5 cm. pig ('02, fig. 2) 5 represents 

 very different conditions; here -are blind, blunt terminals and no 

 sprouts. She stales, however, that occasionally from one of these 

 blunt ends, the "injecting fluid can be forced out into a long 

 thread-like process" which is a sprout and represents the process 

 of growth. 



She has plainly described a somewhat different structure from 

 the solid uninjectible strands of MacCallum and Bartels, though 

 not improbably a phase of the same process. A number of in- 

 terpretations suggest themselves: 



1. Miss Sabin's, that the slender injectible processes are sprouts 

 growing from formed vessels and that this is the only mode of 

 their extension at this period. 



2. That in view of their infrequency, we are dealing with the 

 inception of autonomy on the part of the endothelium, which in a 

 few places is sprouting, while in most it is advancing by accre- 

 tion, as has been definitely proved for the thoracic duct and the 

 systemic lymphatics in general in embryos. 6 



cytodesmata described by v. Szily, Studnicka and others, it is of course void of 

 theoretical importance in this sense, for if in general, elements of different germ 

 layers may stand in syncytial relation to one another, the specificity of endothelium 

 is in no way impaired by a like continuity with the mesenchyme, which in fact it 

 does possesss in the embryo. If in the foetus a separation does actually occur, 

 it ought to be interpreted in the light of the general tendency of the organism to 

 resolve its synctia into independent cells, and not as a peculiar sign of the speci- 

 ficity of endothelium. 



4 1909. Das Lymphgefasssystem. Jena. p. 12. 



5 1902, Am. Jour. Anat. vol. 1, p. 367. 



8 Huntington & McClure, 1907, Am. Journ. of Anat., vol. 6, Abstr. Anat. Rec., 

 vol. 1, pp. 36-41. Huntington, 1908, Anat. Rec. vol. 2, pp. 19-45; 1910, Anat. 

 Rec., vol. 4, pp. 339-423; Compte Rendu 16 Congres Internat. de Med. Sect. 1, 

 fasc. 2, pp. 127-142; Anat. Anz. Erganz. z. Bd. 37, pp. 76-94; 1911, Wistar Mem. 

 No. 1; Anat. Rec., vol. 5, pp. 261-276. Stromsen, 1912, Anat. Rec., vol. 6, pp. 

 343-356. Kampmeyer, 1912, Am. Jour. Anat., vol. 13, p. 401, and Anat. Rec., 

 vol. 6, p. 223; McClure, 1912, Anat. Rec., vol. 6, p. 233. Tilney, 1912, Amer. 



