306 THE SOLIDS. 



dinal section of an ossifying foetal bone, in connexion with 

 its cartilaginous epiphysis, the following particulars will be 

 noticed. 



First, it will be observed that the cartilage cells in the 

 neighbourhood of the bone, instead of being scattered irre- 

 gularly throughout the intercellular substance, are arranged 

 in several consecutive and alternating rows or files, the 

 lowermost of which dip into and are surrounded by osseous 

 cups and septa ; that the cells forming the lower portion of 

 the lowest tier are larger, and less compressed, than those 

 which enter into the formation of the upper part of each 

 lower series, and that they are separated from each other 

 by distinct portions of intercellular substance. Secondly, 

 it will be remarked that the extremities of the still soft 

 bony spiculae invade and extend into the spaces which in- 

 tervene not merely between the rows of cells, but also 

 between the individual cells, and further that granular and 

 probably cytoblastemic particles are deposited in this inter- 

 cellular substance, particularly where this comes into con- 

 tact with the cartilage cells themselves. (See Plate XXXIV. 

 figs. 1. 4.) 



As the process of ossification advances, the cell wall of 

 the cartilage cells becomes absorbed; granular corpuscles 

 are next generated in the primary cancellus, after which the 

 nuclei of the cartilage cells (which are observed to become 

 smaller the deeper they lie in the bone), are removed 

 by absorption ; finally, the small septa intervening between 

 the individual cartilage cells are removed, the larger me- 

 dullary spaces being thus formed. (See Plate XXXIV. 



^4.) 



Furthermore, in these precursory and even in the older 

 spiculae, fibres analogous to those in which the spiculae 

 of the parietal bones are developed may be abundantly 

 detected. 



Such is a brief sketch of the several steps of the intra- 

 cartilaginous form of ossification. 



Now the process which we have just described is con- 

 stantly in progress ; cartilage cells on the one side are con- 



