174 



TEXT-BOOK OF EMBRYOLOGY. 



Endoplasm with 



"white" fibers 



Ground / 



substance jf 



Ectopias l~-~L 



Fig. 150. — Connective tissue cells from intervertebral disk of calf embryo; showing origin of 

 "white" and elastic fibers in protoplasm of cells. Ectoplasm represents a modified part 

 of the protoplasm. Hansen. 



■=■_»■" 



Periosteum 



Osteoblasts 



Periosteum 



Fig. 151. — Vertical section through frontal bone of human foetus of 4 months. 

 (Intramembranous ossification. ) Photograph. 



