170 



TEXT-BOOK OF EMBRYOLOGY. 



Ectoplasm with t 

 "white" fibers ^ "-- 



Ground 

 substance ' 



Ectoplasm / . 



FlG. 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. 



Osteogenetic 

 tissue 



FIG. 151. Vertical section through frontal bone of human fcetus of 4 months. 

 (Intramembranous ossification.) Photograph. 



