DEVELOPMENT OF VASCULAR PLEXUS IN SCALP OF HUMAN EMBRYO. 161 



CONCLUSIONS. 



1. In this paper evidence is presented which shows that the growing edge of 

 the subcutaneous vascular head plexus in human embryos at about the end of the 

 second month is still in the angioblastic stage, and consists of a plexus of cells 

 rather than a plexus of vessels. 



2. The particular area studied was an interesting one for observation of the 

 relation of red blood-cells to endothelium. Such an area is obviously simpler than 

 adult bone-marrow, and though no distinctly angioblastic phase was noted inter- 

 mediate between mesenchymal cells and red blood-cells, the origin of the red blood- 

 cells seemed in direct relation to an advancing vascular zone. These observations 

 indicate the origin of red blood-cells by a process somewhat between an intravas- 

 cular development and an extravascular development, with subsequent entry of the 

 cells into preformed vessels. 



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 Hochstetter, F., 1916. Uber die Vaskularisation der Haut des Sehadeldacb.es menschlicher Embryonen. K. Akad. 



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