

FIG. 167. DEVELOPING BONE IN A PHALANX OF A FIVE MONTHS HUMAN FETUS. 



a, Fetal cartilage ; 6, enlarged cartilage cells ; c, primary bone ; d, periosteum ; e, peri- 

 osteal bone ; /, a thin-walled blood vessel within the marrow cavity ; g, the line points 

 to an osteoclast. Hematein and Congo red. Photo, x 69. 

 178 



