348 SPECIAL HISTOLOGY. 



grow in one direction, and, consequently, is there soon entirely 

 converted into bone, whilst in others its growth continues, so that 

 a new cartilaginous, plastic material is furnished for the pro- 

 gressive increase of the bone, which material, as in the epiphyses 

 of the cylindrical bones, is sometimes developed into distinct 

 ossific centres or nuclei. When the whole of the cartilage has 

 been converted, and its perichondrium become 'periosteum, the 

 bone does not cease to enlarge, but a new and peculiar mode 

 of formation is now set up, in all these places, until its growth 

 is completed. This consists in the ossification, from that surface 

 which is in contact with the bone, of an organised, soft, plastic 

 material, which is deposited on the inner surface of the highly 

 vascular periosteum, and in proportion as this conversion into 

 bone takes place on the one side, fresh, fluid materials for it are 

 afforded by the periosteum on the other. 



§ 103. 



Changes in the ossifying Cartilage. — The active vegetative 

 process in the cartilage-cells when ossification is going on, 

 depends upon this, — that the cells which were hitherto of 

 small size, and contained but few secondary cells, begin to 

 grow, and successive generations of cells to be produced in 

 them, as may, also, be seen at the ossifying margins of 

 bones already existing, in which situation larger cells may be 

 noticed close to the bone, and others, which are smaller in 

 proportion to their distance from it. All the cells which are 

 engaged in the incipient formation of the bone, present clearer 

 and, less frequently, granular contents, a distinct, vesicular, 

 round nucleus, with nucleolus and readily distinguishable 

 walls ; they are very quickly altered, however, on the addition 

 of water, acetic acid, alcohol, and by drying, &c, so that the 

 contents contract around the nucleus, and form a roundish, 

 elongated, irregular, even stellate, granular, opaque body 

 {cartilage-corpuscle Autor). Their size and mode of grouping 

 vary, not inconsiderably, according to age and situation. With 

 respect to the former, they exhibit during embryonic life a 

 constant increase, whilst after birth they appear to retain a 

 uniform size ; and, as regards the latter, it may be stated as a 

 law, that where the ossification of the cartilage proceeds in 

 one direction only, the cells, at the osseous border, are disposed 



