PLATE 1 



EXPLANATION OF FIGURES 



7 A different portion of the obliterated vein shown in figure 6. X630. 



8 Umbilical vein of the dog; same as figures 6 and 7 but somewhat farther 

 centrally. X450. 



9 Portion of wall of umbilical vein of dog 45 hours old, showing process of 

 degenerating media extending into the lumen. X750. 



10 From the same vessel as figure 9, showing process formation, vacuolation 

 beneath the endothelium and vascularization of the process. X750. 



11 Omphalomesenteric vessel from a dog 44 hours old, showing degenerating 

 endothelium and media and some ill-preserved blood in the lumen. X7.50. 



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