EXPERIMENTAL STUDIES ON THE ORIGIN OF VAS- 

 CULAR ENDOTHELIUM AND OF ERYTHROCYTES 



FRANKLIN PEARCE REAGAN 



Laboratory of CoiJiparative Anatomy, Princeton University 



EIGHTY-NINE FIGURES 



CONTENTS 



Introduction " 40 



Part I 



The Origin of Endothelium 



I. The Angioblast theory 41 



II. The Local Origin theory 44 



III. Summary of the experimental work 48 



1. Graper's work 50 



2. The work of Hahn, and of Miller and McWhorter 56 



IV. Material, methods and observations 60 



1. Chick material and mechanical methods 60 



a. Refinements of the technique 61 



b. Complete isolation of meroplasts 63 



c. Incomplete isolation of meroplasts 68 



d. Splanchnopleural concrescence and the mechanics of heart for- 



mation 70 



e. A possible interpretation of certain mesothelial funnels and 



multiple hearts 74 



f. The dorsal aorta 79 



g. Endothelium independent of mesothelium 80 



2. The origin of the pre vascular mesoderm 81 



a. Visceral mesoderm 81 



b. Parietal mesoderm 83 



c. Cardiac endothelium from entoderm? 83 



3. The origin of endothelium in hybrid teleosts 88 



4. The endothelium of chemically treated embryos 89 



5. Observations on the living material 89 



36 



