482 LECTURE XIX. 



no doubt true, that in the case of the normal growth in 

 length of bone most of the bone-corpuscles do not directly ^ 

 proceed from cartilage-corpuscles, but are immediately 

 derived from marrow-cells and only mediately from 

 cartilage-cells ; but it is just as true that cartilage -cells 

 also can be transformed straightway into bone-cor- 

 puscles. It is now a long time since I called attention 

 to one spot in particular, where the conversion of carti- 

 lage into osteoid tissue can be very distinctly viewed, 

 namely at the points of transition from cartilage to peri- 

 chondrium in the neighbourhood of the border of calcifi- 

 cation of growing bones. Here the boundaries between 

 the different forms of tissue are completely obliterated, 

 and all sorts of transitions between round (cartilaginous) 

 and jagged (osteoid) cells are seen. 



The next preparations have reference to the patholo- 

 gical new formation of bone, or, if you will, to the physio- 

 logical formation of callus. They are derived from a 

 very recent fracture of the ribs, around which a thick 

 mass of callus has been deposited. In reference to this 

 process I will add a few words, as it is one "that has been 

 much discussed and is very important in a surgical point 

 of view. 



You have seen from what I have just been describing 

 to you, that thjere are several ways in which the new 

 formation of bone is effected, and that the old supposi- 

 tion that either the one or the other mode must be 

 considered as the only prevailing one, is incorrect. 

 The pre-existence of cartilage is by no means necessary 

 for the formation of bone ; on the contrary, an osteoid 

 substance is very frequently formed by a direct sclerosis 

 in connective tissue, nay ? ossification is thus really more 

 easily effected than when it takes place in real cartilage. 

 We see also by the history of the theories concerning 

 callus, that the endeavour to show that it is always 



