CAETILAGE. BONE. TEETH. 35 



the section, it is to be observed that its cells are dis- 

 posed in parallel rows, and that some of them are 

 quite altered in appearance. One portion of them 

 differs in no respect from ordinary cartilage cells, 

 whilst the remainder have already changed in form, 

 the change being confined mainly to their nuclei. 

 The nucleus, for example, has become very irregular 

 in its outline, and by sending out prolongations in 

 every direction, has put on a decided resemblance to 

 a bone-cell. It is imbedded in a finely granular sub- 

 stance limited by a pale circular or oval line, the cell 

 wall ; outside of this another line is to be seen in 

 close proximity to the first, and surrounding the cell ; 

 this is the capsule of the cartilage cell. (PL VI. fig. 

 III. 2, 3, 4.) 



In view of these facts it is pretty evident that the 

 osseous cell, or lacuna, is identical with the nucleus 

 of the original cartilage cell, in a more advanced 

 stage of development. 



The process of ossification is completed by the 

 elongation of the filiform prolongations, or canaliculi, 

 given off from the nuclei of the cartilage cells, which 

 terminate by anastomosing with the canaliculi of 

 neighboring nuclei ; and meanwhile earthy salts have 

 been brought by the bloodvessels and deposited in 

 the fundamental substance of the cartilage, as well as 

 in the interior of its cells. Neither the walls of these 

 cells, nor their enveloping capsule, disappear imme- 

 diately after the ossification of their contents ; by the 

 addition of dilute hydrochloric acid to a portion of 

 recently ossified bone they can both be rendered 

 visible prssenting their usual appearance. 



