30 VASCULOGENESIS IN THE CAT 



Aus alien diesen Angaben geht also hervor, dass die freien Elemente 

 der Lymphknoten an Ort und Stelle entstehen und zwar wie iiberall aus 

 abgerundeten und losgelosten Mesenchymzellen, die eine bestimmte Zeit- 

 lang auch hier die Fdhigkeit haben, sich in der Richtung der roten und 

 weissen Blutkorperchenreihe zu differenzieren 56 



In Connective Tissue: 



Als wesentliches Resultat aller dieser Untersuchungen ergibt sich 

 also, dass dem embryonalen Bindegewebe zundchst im weitesten Umfange 

 die Fdhigkeit zukommt, aus seinen Mesenchymzellen freie bewegliche 

 Blutzellen zu bilden, die den Typus der primitiven Blutelemente aufweisen 

 und sich anfanglich sowohl in der Richtung der Erythrocyten wie der 

 Leucocyten differenzieren konnen. 67 



The doctrine of specificity has found its support in phenomena 

 of growth, chiefly in the solid terminations of lymphatics which 

 are observed in rather late periods of ontogeny, and the avoidance 

 of these sprouts by mesenchyme cells in the tail of the tadpole. 

 The former fact has been by implication projected into earlier 

 stages of development, and into peripheral regions which are not 

 accessible to the method of injection. The latter has been erect- 

 ed into a general principle of vascular development, in spite of 

 facts of diametrically oppposite import, both in the frog (Goette, 

 Marshall, Morgan, Studnicka) and in other transparent embryos 

 (Wenkenbach, Raffaele). 



The theory of adaptation rests upon the observation of the 

 transformation of mesenchyme cells into endothelium in a large 

 number of forms at various periods of ontogeny, ascertained by 

 a variety of methods and by observers with very different prob- 

 lems in view; second on the reversion of endothelium to mesen- 

 chyme (v. Szily, Huntingdon, Mall) : and third, on the commu- 

 nity of products and the permutability of endothelium, blood 

 cells and mesenchyme (Maximow, Dantschakoff , Mollier, Weiden- 

 reich et al.). 



The doctrine of the angioblast is so closely entwined with that 

 of the specificity of endothelium that there is little promise in 

 an attempt to consider it separately, especially as this conception 

 of vasculogenesis loses its chief raison d'etre with the recognition 

 of the plasticity (non-specificity) of endothelium. As presented 



66 Ibid, p. 203. " Ibid, p. 205. 



