DEVELOPMENT OF THE VASCULAR SYSTEM 



523 



formed in the ventral part of the sagittal plexus. As the hemispheres extend back- 

 ward these sinuses elongate by incorporating the more caudal loops of the plexus. 

 The anterior part of the sinus is completed first. 



PLEXUS MEOIAJJS 



V 



FIGS. 481 to 488. Profile drawings of the dural veins showing principal stages in their development in human 

 embryos from 4 mm. to birth. It is of particular interest to notice their adaptation to the growth and changes in the 

 form of the central nervous system. Fig. 481, 4 mm.; Fig. 482, 14 mm.; Fig. 483, 18mm.; Fig. 484, 21 mm.; Fig. 485, 

 35 mm. ; Fig. 486, 50 mm. crown-rump length; Fig. 487, 80 mm. crown-rump length; Fig. 488, adult. (After StreeterJ 



W mill. , 4 1. - 



