4.58 LECTURE XVIII. 



rapidly yield up its fat, the elements may divide and we 

 then again have red, but inflammatory, marrow. 



In this whole series of allied processes from the first 

 development of marrow out of cartilage until the pro- 

 duction of inflammatory marrow the last disturbance 

 which manifests itself in injured bones (as we see in 

 amputations) there at no time exists any amorphous 

 substance, blastema or exudation ; we can always trace 

 the descent of one cell from another ; every one of them 

 has been directly developed from an earlier one, and 

 will have as long as the proliferation continues, a direct 

 progeny of cells. 



The second series of transformations in the longitudi- 

 nal axis of the cylindrical [long] bones is furnished by 

 the osseous tissue, which may arise out of marrow and 

 cartilage. In the one case the marrow-, in the other, 

 the cartilage-cells, become the subsequent bone cells. 

 This act of real ossification, the production of the osse- 

 ous tissue, is extremely difficult to observe, chiefly for 

 the reason, that what first takes place in the course of 

 these processes, is not the production of real osseous 

 tissue, but only the deposition of calcareous salts. Gene- 

 rally, namely, there first of all takes place in the imme- 

 diate vicinity^of the border of the bone a calcification 

 of the cartilage, which gradually advances, first along 

 the borders of the larger groups of cells, and then 

 around the individual cells, always following the sub- 

 stance of the capsules, so that every individual cartilage- 

 cell is surrounded by a ring of calcareous substance. 

 But this is not yet bone, it is nothing more than calcified 

 cartilage, for, upon dissolving the calcareous salts, the 

 old cartilage is again brought into view and indeed it 

 offers no analogy to bone in any other respect excepting 

 in the presence of calcareous salts. 



Now, in order that this calcified cartilage may become 



