BONE TISSUE. 6$ 



former tissue into the latter was unhesitatingly accepted. 

 Sharpey, Bruch, H. Mueller, first demonstrated the erro- 

 neousness of this hypothesis. 



Disregarding rare exceptions, the facts run, nowadays, in 

 this way : The calcified cartilage does not become osteoid 

 tissue, but rather melts down, and in the system of cavities 

 thus obtained, the bone substance produced by the peri- 

 osteum is established as a new tissue. 



If we take a cartilage which is destined to end in this man- 

 ner, two different processes are presented : 



i. A local softening of the cartilage tissue (of the cells as 

 well as of the intercellular substance) has taken place from the 

 surface in an inward direction. Very irregular, manifoldly 

 ramified passages have thus been formed. Vessels have 

 grown into the latter from the perichondrium, accompanied 

 by lymphoid and unripe connective-tissue cells. This sub- 

 stance has been not badly named the cartilage marrow. 

 Until recently, it was erroneously assumed that the so-called 

 cartilage marrow cells represented derivatives from cartilage 

 cells which had penetrated the softened portion. 



2. In the centre of such a cartilage, a calcification of the 

 intercellular substance (p. 44) and very generally, also, an 

 energetic forma- 

 tion of so-called „ * /"/^©^C-o©^^ rx 



|«l :mmj r m 



occurs (Fig. 62). .^3«SP r 



This place has KM WW 



been called the IW^^^^M 



point of ossifi- (ftMtes«-«#*M«eHM 



rn h'nn K o A 1 ir ¥ig. 62. — Dorsal vertebra of a human foetus of ten weeks in vertical 



Cciuuil UdUiy section, a, calcified ; b, soft cartilage. 



enough, we add. 



For, although a further melting down of the calcified tissue 

 occurs here forthwith, and, in the spaces thus formed, the first 

 deposition of osteoid tissue commences immediately after- 

 wards, this calcified cartilage has nothing whatever to do with 

 the latter. 



The two metamorphoses just mentioned proceed rapidly 



