36 CARTILAGE. BONE. TEETH. 



It is asserted by some observers that it is the car- 

 tilage cells themselves, and not their nuclei, which 

 are thus transformed into bone cells. They describe 

 the cell-wall as becoming wrinkled, and undergoing 

 the changes which we have attributed to its nucleus, 

 whilst the nucleus itself fades away and finally dis- 

 appears entirely. (PL VIL fig. II.) In opposition to 

 the authorities by whom this statement is endorsed, 

 we are disposed to persist in the belief that it is the 

 nucleus of the cartilage cell which becomes trans- 

 formed into the osseous cell, or lacuna, of bone. 

 F<etai Marrow. The cells of ossifying cartilage which remain un- 

 changed during the process just described, eventually 

 assume the character of foetal marrow. At first they 

 become the seat of active endogenous development, 

 in consequence of which they increase, together with 

 their enveloping capsules, very considerably, in size. 

 PL VI. fig. IV. 4.) Very soon they come in contact 

 with each other, their capsules becoming welded 

 together (PL IV. 5), and the partitions which thus 

 result, melting away as they lie arranged in longi- 

 tudinal rows, a medullary canal is thus formed filled 

 with young cells and free oil-globules, w r hich, in fact, 

 constitutes foetal marrow. (PL IV. 6.) Whilst the 

 process of ossification is going on, numerous blood- 

 vessels derived from its perichondrium are seen 

 ramifying through the substance of the cartilage. 

 These seem at first to be simply hollowed out of the 

 cartilage ; but later in the process the cartilage cells 

 immediately around them become elongated and fusi- 

 form in shape, and seem by their subsequent union 

 to form walls for the vessels. 



