VASCULOGENESIS IN THE CAT 17 



by the evidence which is alleged to support them. The method 

 is partial in that it excludes a vasculogenetic periphery beyond 

 its limit of exploration, uncritical in that it can only reveal 

 permeability and not the structure of the vessel wall, and its 

 advocates are inconsistent in that without just grounds they in- 

 terpret its only peculiar datum, the extravasation, as an artifact. 



Nor does the doctrine of specificity receive more support from- 

 observations intra vitam, if we distinguish between the growth 

 and the formation of a tissue, and refrain from transferring proc- 

 esses recorded of a given stage, perhaps a late one, to earlier 

 periods in ontogeny. 



The observations upon the tails of amphibia, especially the 

 tadpole, a classical object since the days of Schwann, have accu- 

 mulated a rich fund of observations regarding the sprouting both 

 of blood vessels and of lymphatics. Kolliker, 21 Rouget 22 and 

 Golubew 23 followed the process, step by step, describing the hol- 

 low-pointed outgrowth, its acquisition of a lumen and its fusion 

 with adjacent sprouts. The sprouts were found to arise, not 

 only in the vicinity of nuclei but also at a distance from them 

 (Kollicker, Flemming); 24 in the latter event nuclei were found 

 subsequently to move into the sprouts (Fleming, Bobritski). 25 

 v. Ebner, in his edition of Kolliker's Handbuch, summarizes these 

 findings and interprets them correctly as phenomena of growth: 



Die Sprossung muss demgemass als ein Wachsthumsvorgang des 

 Protoplasma angesehen werden, denn auch in den Fallen, wo der Kern 

 an der Sprossungsstelle liegt, lasst sich zunachst nichts von einer Kern- 

 theilung sehen. Man muss wohl die primaren Sprosse als sich aushohl- 

 ende Protoplasmaknospen einer Endothelzelle ansehen. Erst sekundar 

 erfolgt dann eine Mitose in der Zelle des Muttergefasses und der eine 

 Tochterkern tritt nachtraglich und nachdem er bereits wieder zu einem 

 ruhenden Kerne geworden, in den Gefassspross, der unterdessen weiter 

 gewachsen ist, ohne dass eine Zelltheilung erfolgt, da man, wie bereits 

 erwahnt wurde, in jungen eben sich bildenden Kapillaren keine Zell- 

 grenzen nachweisen kann. 23 



' 21 1846, Ann. S. sc. natur., T. v. p. 91. 1886, Zeitschr. f. wiss. Zool., Bd. 43, p. 1. 

 22 1873, Arch, de Physiol. 

 23 1869, Arch. f. mikr. Anat., Bd. 5, p. 49. 

 24 1890, Arch. f. mikr. Anat., Bd. 35, p. 283. 



25 1885, Central bl. f. mikr. Anat. 



26 Loc. cit., p. 672. 



MEMOIR NO. 3 



