CONTENTS. 



PAOE. 



Introduction , ........,....;.... i .>J ,., . ........ .: .^...- 7 



Establishment of primordial vascular system of head 9 



Differentiation of primordial system into arteries, veins, and rapilUuies 11 



Cleavape of blood-vessels of head into separate systems 10 



Adjustments of blood-channels in adaptation to growth and change in form of brain and ear 21 



Development of superior sagittal sinus 30 



Summary 34 



References cited 38 



Explanation of plates 38 



6 



